How to Redline a Drawing the Right Way (9 Markup Conventions)
Short answer: To redline a drawing the right way, mark each issue with the tool that fits it — a pin to flag a point, a rectangle or revision cloud to bound an area, an arrow or leader to connect a note to its target, a highlight to draw the eye, freehand for a sketched correction, a text note for the comment itself, a callout for a structured instruction, and a stamp for a status decision — using consistent colour and line weight so the meaning is unambiguous. Archi Check ships exactly these nine markup tools, and every markup becomes a tracked comment with an owner and a status.
Redlining is the oldest quality-control habit in architecture. Someone prints a drawing, reaches for a red pen, and marks every place the set is wrong, unclear, or unresolved. The colour gave the practice its name: red ink stood out against black linework, so a reviewer's corrections could not be mistaken for the drawing itself. The principle has outlived paper — whether you mark up on a printout or on screen, a redline is still a layer of meaning placed on top of a drawing, and its whole value depends on being read correctly by the person who has to act on it.
The problem is that redlining looks simple and rarely is. A reviewer who scrawls a vague cloud and the word "fix" has technically marked the drawing, but they have not communicated anything useful. Good redlining is a small discipline with its own conventions: which tool to use for which kind of issue, what each colour means, how heavy a line should be, and — most importantly — the difference between marking that something is wrong and describing what would make it right. This guide sets out the nine markup conventions a reviewer actually uses, and how to keep them legible enough that nobody has to guess.
What redlining actually is
A redline is an annotation layer, not a change to the drawing. The author owns the linework; the reviewer owns the markup. When a reviewer redlines a sheet, they are not editing it — they are recording observations and instructions the author will use to revise the original. Keeping the two separate is the first convention, and the reason red ink was chosen in the first place: a correction that blends into the drawing is a correction nobody can find.
That is why a markup needs to be unambiguous in three ways at once. It has to be visible, so it is not missed. It has to be specific, so the reader knows exactly which part of the drawing it refers to. And it has to be intelligible, so the reader knows what the marker meant. A red cloud floating in empty space near a wall fails the second test; a note that says "wrong" fails the third. The conventions below exist to satisfy all three.
It is worth being clear about what a redline is for, too. The purpose is not to prove the reviewer read the drawing — it is to get the set corrected and re-checked. A markup the author cannot act on is wasted effort, and one that is never closed out is worse than none, because it creates a false record that the issue was handled. Redlining is the opening move of a quality loop, not the end of one.
Why markup conventions matter
Conventions exist to remove guesswork. On any project larger than one person, a marked drawing will be read by someone else — the author who corrects it, a second checker who verifies it, a colleague who picks up the set when the original reviewer is on leave. If every reviewer invents their own visual language, the markup only makes sense to the person who drew it, and the moment they are unavailable the redlines become a puzzle.
The most important conventions attach meaning to appearance. When colour carries meaning, a reader can triage a sheet at a glance: red is a correction that must be made, a different colour is a query or coordination note, another marks something already resolved. When line weight is consistent, a heavy mark reads as important and a light one as minor, rather than as an accident of which pen was nearest. When a tool always means the same kind of issue, the reader does not have to interpret intent. The goal is that anyone in the office can pick up a marked set and read it the same way the marker did.
The opposite — a free-for-all where everyone marks differently — is one of the quiet causes of QC failure. A markup that is misread is worse than one that is missed, because the author confidently makes the wrong change. Conventions are cheap insurance against that.
Colour conventions
Colour is the fastest signal on a marked drawing, so it should carry the most stable meaning. The traditional three-colour scheme is a good starting point: red for the reviewer's corrections, a second colour — often blue or green — for queries or the author's responses, and a third — frequently yellow as a highlight — for items that have been checked or resolved. The classic checking convention is even simpler: a checker marks corrections in one colour, and a second person "backs off" each item in a different colour as it is confirmed corrected, so when the whole sheet is the second colour the check is done. The exact palette matters less than the rule that the office agrees on one and uses it everywhere — and on screen those colours become properties of a markup rather than physical pens, which means a tool can enforce them.
Line-weight conventions
Weight is the second signal. A heavy line reads as emphatic and a fine line as a detail, and a reader uses that without thinking. The convention is to keep weight meaningful rather than decorative: a consistent medium weight for ordinary markups so the drawing underneath stays readable, heavier weight reserved for items you genuinely want to stand out, and no lines so thick they obscure the linework you are commenting on. A redline that hides the thing it is correcting defeats itself.
The nine markup conventions
Almost every redline a reviewer places is one of nine kinds of mark. Each answers a different question — where is the issue, what does it cover, what should change, what is the status — and each has a tool that fits it. These are the nine tools Archi Check provides, because between them they cover the full range of what a reviewer needs to say.
Pin
A pin marks a single point: "look here." It is the lightest possible markup, and the right choice when the issue is located at a precise spot rather than across an area — a missing dimension at one node, a clash at one junction, a symbol in the wrong place. The pin's value is that it anchors a comment to an exact coordinate on the sheet, so the reader is never left wondering which of three similar details the note refers to. Use a pin when the location is the whole story and you will describe the issue in the attached note.
Rectangle
A rectangle bounds an area: "this region, specifically." Where a pin marks a point, a rectangle marks a zone — a portion of a plan that is missing information, a detail that needs reworking, a block of schedule that is wrong. It is cleaner than a freehand outline when the area is roughly rectangular, which most drawing regions are, and it reads as deliberate. A rectangle says the reviewer has consciously scoped the issue to everything inside the box and nothing outside it.
Revision cloud
The revision cloud is the most recognised markup symbol in the industry, and it has a specific meaning: this area has changed, or must change. The scalloped outline is deliberately attention-grabbing and impossible to mistake for linework. On an issued drawing a cloud usually flags what was revised between versions, often paired with a revision tag; in review, a reviewer uses it to bound the region that needs revision. The convention is to cloud the smallest area that fully contains the change, and to remove superseded clouds on the next revision so the drawing does not accumulate them.
Arrow / leader
An arrow or leader connects a comment to its target: it answers "which part does this note refer to?" when the note itself sits in clear space. A leader is the difference between a comment that floats ambiguously and one that points unmistakably at the thing it concerns. The convention is for the arrowhead to land precisely on the feature in question and for the line to be clear of other linework so the connection is obvious. Leaders are what make text notes usable on a dense drawing, because they let you place the words where there is room and still tie them to a crowded detail.
Highlight
A highlight draws the eye without obscuring anything underneath. Because it is semi-transparent, it is the tool for emphasis rather than correction — marking the runs of wall that share a problem, the rooms affected by a coordination issue, or, in the classic checking convention, the items that have been verified. The convention is to use highlight for "pay attention to this" or "this is done," not for "this is wrong," and to keep the colour consistent with whatever your palette assigns it. A highlight that changes meaning from sheet to sheet is noise.
Freehand
Freehand is the sketch tool: the reviewer draws what they mean. When a correction is geometric — a wall that should move, a line that should curve, a route the drawing got wrong — words are slower and less clear than a quick sketch over the top. Freehand is also how a reviewer indicates a proposed change rather than just flagging a problem, which is a real distinction covered below. The convention is to keep freehand legible and clearly a markup, not a redrawn line that could be mistaken for the author's own work, which is exactly why the contrasting colour matters.
Text note
The text note carries the actual words. Every other tool locates or bounds an issue; the text note says what the issue is. This is where the discipline of redlining lives, because a good note is specific and actionable and a bad one is neither. "Door swing clashes with the radiator — confirm clearance or reposition" is a note the author can act on; "wrong" is not. The convention is to write the note so the reader knows both the problem and what resolving it would look like, and to attach it to a pin, leader, or shape so its location is never in doubt.
Callout
A callout is a structured note — typically a boxed or bubbled annotation with a leader — used when a comment needs more than a loose line of text. Where a plain text note suits a quick remark, a callout suits an instruction you want to read as a discrete, framed item: a numbered comment that maps to a review schedule, a coordination instruction that crosses disciplines, a correction important enough to deserve its own box. The convention is to use callouts consistently for the comments that need to stand as formal items, so they are visually distinct from casual notes and easy to enumerate.
Stamp
A stamp records a status, not a correction. Where the other eight tools mark issues within a drawing, a stamp makes a statement about the drawing as a whole — APPROVED, REVISE, REJECTED, FOR REVIEW, AS BUILT. It is the reviewer's decision, placed in the corner, that tells the recipient what they may now do with the set. The convention is that a stamp is the last mark, applied once the issues are marked and the decision is made, and that its wording is chosen carefully because it carries responsibility. For the full meaning of each stamp, see drawing approval stamps explained.
Choosing the right tool: a quick reference
The fastest way to internalise the nine is to map them to the question each one answers. A redline is usually a combination — a pin or shape to locate, a leader to connect, a text note or callout to explain — rather than a single mark.
| Tool | What it answers | Use it when |
|---|---|---|
| Pin | Where, exactly? | The issue is at a single precise point |
| Rectangle | Which area? | The issue covers a roughly rectangular zone |
| Revision cloud | What changed or must change? | Bounding a region that has been or must be revised |
| Arrow / leader | Which part does this refer to? | A note sits in clear space and needs to point at its target |
| Highlight | What deserves attention or is done? | Emphasis or marking verified items, without obscuring linework |
| Freehand | What should this look like? | A geometric correction is quicker to sketch than to describe |
| Text note | What is the issue? | The comment itself — the problem and the fix in words |
| Callout | What is the formal instruction? | A structured, enumerable comment that should stand as an item |
| Stamp | What is the status? | Recording the decision on the drawing as a whole |
Keeping markups legible
A marked drawing competes for space with the drawing underneath it, and legibility is easy to lose. The goal is for a reader to separate, at a glance, the linework from the markup and one markup from another.
Place text where there is room and use a leader to reach the target, rather than cramming words into a dense detail. Keep markup colour in contrast with the drawing — the reason red works on black-and-white linework is contrast, and a markup colour that matches the drawing disappears. Avoid stacking markups; if an area needs several comments, space them and lead each to its point rather than overlapping them into an unreadable knot. And resist over-marking: a sheet covered in redlines is as hard to act on as one with none, because the author cannot tell the critical comment from the trivial one. Mark what matters, weight it so importance reads at a glance, and leave the drawing visible.
Marking a problem vs describing the fix
This is the convention that separates a useful redline from a frustrating one. There are two different things a markup can do, and a reviewer should know which they are doing. Marking a problem says "this is wrong" — it identifies the issue and leaves the solution to the author, who owns the drawing and usually knows best how to resolve it. Describing the fix says "do this specific thing" — it prescribes the change.
Both are legitimate, but they are not interchangeable, and confusing them causes friction. A reviewer who sketches a precise freehand correction for an issue with several valid solutions oversteps and may impose a worse fix than the author would have chosen. One who writes only "wrong" on a genuinely ambiguous detail leaves the author guessing and invites another round of review. The discipline is to mark the problem clearly in every case, and to describe the fix only when there is a specific required outcome — a code clearance, a client standard, a coordination constraint — that the author needs to meet.
In practice this maps onto the tools. A pin and a clear text note that names the problem is the default; a freehand sketch or a prescriptive callout is the right escalation when the fix is not optional. Knowing which mode you are in, and marking accordingly, is what makes a redline read as a collaboration rather than a correction handed down.
A worked example
To see the conventions working together, here is how a reviewer might mark a single issue on a floor plan — an accessible WC that looks too tight — using several tools in combination rather than one mark.
- Pin placed at the centre of the WC, anchoring the comment to the exact room.
- Rectangle bounding the WC and its door swing, scoping the issue to that zone.
- Leader from a clear area of the sheet into the room, so the note has space to be read.
- Text note at the end of the leader: "Clear turning circle appears below the required diameter — confirm against accessibility standard or enlarge the room."
- Highlight, in the office's "query" colour, over the adjacent rooms that would be affected if the WC grows, flagging the knock-on coordination.
- Stamp of REVISE in the corner, recording that the sheet is not accepted and must come back.
Notice that the reviewer marked the problem — a turning circle that looks short — without dictating the fix, because there are two valid resolutions and the author should choose. The redline is specific about the issue, clear about its location, honest about the knock-on effects, and unambiguous about the status of the sheet. That is what the conventions are for.
Where Archi Check fits
Archi Check is purpose-built QC software for architectural drawing sets, and it ships exactly these nine markup tools — pin, rectangle, revision cloud, arrow, highlight, freehand, text, callout, and stamp — each with colour and line-weight properties you can set to match your office conventions. So the colour scheme and weights this guide describes stop being a habit you hope people follow and become properties of the markup itself, consistent across every reviewer and every sheet.
The more important part is what happens after you place a mark. In Archi Check every markup is not just ink on a layer — it is a tracked comment with an owner and a status that moves through Check → Correct → Verify → Close. A reviewer places a pin and a note in the Check stage; the comment is assigned to whoever owns the fix; when the change is made, someone other than the author verifies it; only then does it Close, with a record of what changed and who signed it off. A redline cannot quietly disappear, because it stays open until it is closed out — precisely the failure mode that loose markup invites.
The workflow suits the way reviewers actually work: a two-screen setup with the register on one monitor and full-size drawing markup on the other, so you mark up at scale while every comment is tracked beside you. Because Archi Check keeps your QC data in your own project folders rather than a vendor cloud, the markups and the audit trail belong to you. Archi Check runs on Windows today, with macOS coming soon, and there is a 14-day free trial.
FAQ
What does it mean to redline a drawing?
Redlining a drawing means adding a layer of markup — corrections, queries, and notes — on top of the original to record what is wrong, unclear, or unresolved, without changing the drawing itself. The name comes from the traditional use of red ink so the reviewer's marks stand out against the black linework. The author of the drawing then uses the redlines to revise the set, and the markups are checked off as each issue is resolved.
Why do redline markup conventions matter?
Conventions matter because a marked drawing is almost always read by someone other than the person who marked it. When colour, line weight, and tool choice carry consistent meaning, any reader can triage and act on a sheet the same way the reviewer intended. Without conventions, the markup only makes sense to its author, and a misread redline is worse than a missing one because it leads the author to make the wrong change confidently.
What do the colours mean when redlining a drawing?
The exact palette varies by office, but the common scheme uses red for the reviewer's corrections, a second colour such as blue or green for queries or the author's responses, and a highlight colour such as yellow for items that have been checked or resolved. The classic checking convention has one person mark corrections and a second "back off" each item in a different colour as it is confirmed. What matters is that the office agrees on one palette and applies it everywhere.
What is the difference between marking a problem and describing the fix?
Marking a problem identifies that something is wrong and leaves the solution to the author, who owns the drawing. Describing the fix prescribes a specific change. Both are valid, but they are not interchangeable: mark the problem clearly in every case, and describe the fix only when there is a required outcome — a code clearance, a client standard, a coordination constraint — that the author must meet. Over-prescribing imposes solutions; under-describing leaves the author guessing.
Which markup tool should I use for each kind of issue?
Use a pin for a single precise point, a rectangle to bound a roughly rectangular area, a revision cloud to flag a region that changed or must change, an arrow or leader to connect a note to its target, a highlight for emphasis or to mark verified items, freehand to sketch a geometric correction, a text note for the comment itself, a callout for a structured formal instruction, and a stamp to record the status of the drawing as a whole. Most redlines combine several — a pin or shape to locate, a leader to connect, and a note to explain.
Make every redline a tracked decision
Redlining only improves a set if the marks are read correctly and followed through to a fix. If your markups still live as loose ink that nobody closes out, see how Archi Check turns each one into a tracked comment with an owner, a status, and a full audit trail: Try Archi Check free for 14 days.
Related guides
Keep building out your drawing QC process with Archi Check and these related guides:
- Drawing markup symbols explained
- Drawing approval stamps explained
- Defect tracking on drawings
- The drawing QA/QC process in 4 stages
Archi Check is an independent product by Archi for architectural drawing QA/QC. Product names and trademarks referenced belong to their respective owners and are used for identification only.
