TRIM

Clean up your geometry like a pro.

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Learning objective

By the end of this lesson you can run the TRIM command and cleanly remove overshoots between intersecting objects.

What TRIM is

TRIM shortens an object so it ends precisely at a cutting edge — another object that crosses it. Anything you click between (or beyond, depending on mode) cutting edges is removed.

Why and when you use it

Use TRIM whenever lines, arcs or circles run past where they should — a typical case is cleaning a tic-tac-toe grid down to a plus sign, or cutting a doorway out of a wall.

Where to find it in the AutoCAD interface

Ribbon: Home tab → Modify panel → Trim button.
Menu: Modify menu → Trim.
Command line: Type TRIM and press Enter.
Alias / shortcut: TR (then Enter).

Key vocabulary

Cutting edge: An object that defines where the trim happens. Any other object that crosses the segment you want to remove qualifies.
Object to trim: The portion of geometry you click to remove. It must lie between cutting edges (Standard mode) or anywhere along the line (Quick mode).
Quick mode: The default in modern AutoCAD: every visible object acts as a cutting edge; you just click what you want gone.
Standard mode: Classic behaviour: you first pick cutting edges, press Enter, then click segments to trim.
EXTEND: The reverse of TRIM — lengthens an object to meet another.

Before you start

Open a fresh drawing and draw two LINEs that clearly cross each other.
Make sure OSNAP is on (F3) so future picks behave well.
Note which TRIM mode you're in. Default in AutoCAD 2024+ is Quick.

Step-by-step instructions

1
Set up two crossing lines
2
Start the TRIM command
3
Click the segment(s) you want to remove
4
End the command
5
Switch to Standard mode if needed

Visual reference

Common mistakes & fixes

In Standard mode, pressing Enter only once and getting no result.
Fix: Press Enter TWICE — the second Enter selects every visible object as a cutting edge.
Clicking a segment that has no cutting edge crossing it.
Fix: Make sure another object actually crosses the segment, or use EXTEND if you wanted to lengthen instead.
Trimming the wrong side.
Fix: Press Ctrl + Z to undo just the last trim without leaving the command, then click the correct piece.

Troubleshooting

Nothing happens when I click.Show

Cause: Your cursor is not on a trimmable segment, or there is no cutting edge.

Fix: Hover until the segment previews grey, or add an intersecting object first.

TRIM removed too much / a whole line vanished.Show

Cause: There were no cutting edges between the start and end of the line.

Fix: Press Ctrl + Z inside the command to undo, then draw the cutting object first.

I am in the wrong mode and want classic behaviour.Show

Cause: AutoCAD remembers the last mode used.

Fix: Inside TRIM type O, Enter, S, Enter to switch to Standard.

Practice exercise

Tic-tac-toe → Plus sign

Draw four LINEs that form a # (tic-tac-toe) shape.
Run TRIM (TR, Enter).
Click each of the eight overshoot segments around the central square.
Press Enter to finish.

Success looks like: Only the central plus sign remains — every overshoot is gone, no gaps, no stray lines.

Pro tips & related commands

Pro tips

Hold Shift while clicking inside TRIM to EXTEND instead of trim — one command, two behaviours.
Use the Fence option (type F inside TRIM) to draw a line that trims every object it crosses in one drag.
Use the Crossing option (type C) to box-select many segments to trim at once.

Related commands

EXTEND(EX)
Lengthen an object to meet another — the inverse of TRIM.
ERASE(E)
Delete an entire object outright.
BREAK(BR)
Split an object at one or two specified points.

Lesson quiz

0/3 correct

Score at least 3/3 to unlock lesson completion.

1. In Standard mode, how many times do you press Enter to select 'all' as cutting edges?

2. In Quick mode (default in modern AutoCAD), what acts as a cutting edge?

3. Holding Shift while clicking inside TRIM does what?

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