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BeginnerFree AutoCAD course about 12 min

Trim and extend

Drafting is often “draw long, then trim back”. TRIM and EXTEND tidy intersections in seconds and are among the most used editing commands.

In this lesson you will

  • Trim objects back to other objects
  • Extend objects to meet boundaries
  • Use Quick and Standard modes
  • Switch between trim and extend with Shift

What they do

TRIM (TR) cuts away the part of an object that crosses another. EXTEND (EX) lengthens an object until it meets another. Together they turn rough, overlapping lines into a clean drawing.

Left: two horizontal lines cross a vertical boundary line; the parts beyond the boundary are removed by Trim. Right: two short horizontal lines stop before the boundary; Extend lengthens them until they meet it.Trimremovedcutting edgeExtendaddedboundary edge
Figure: Trim and extend against a boundary. Original KitWren diagram.

Quick mode (the default in recent versions)

If a clicked segment has no cutting edge, Quick mode deletes the whole object — handy for tidying, surprising the first time.

  1. 1Type TR and Enter.
  2. 2Click each piece you want removed. Every other object acts as a cutting edge automatically.
  3. 3Drag a freehand path (press and drag) to trim many pieces at once.
  4. 4Press Enter to finish.

Standard mode: choosing edges

For complex drawings choose the cutting edges yourself: start TRIM, type O (mode) › S (Standard), select the edges, press Enter, then click the pieces to remove. Older versions work this way by default; pressing Enter at Select objects makes everything an edge.

The Shift switch

Inside TRIM, hold Shift and click to extend instead; inside EXTEND, hold Shift to trim. You rarely need to leave one command to use the other.

Extending to an imaginary intersection

If a line would meet a boundary only when extended, use the Edge option (E › Extend) so the boundary is treated as infinitely long. Without it, the two objects must actually cross.

Quick reference

Command / toolHow to start itWhat it does
TRIMTRRemoves parts beyond cutting edges
EXTENDEXExtends objects to boundaries
BREAKBRBreaks an object between two points
FILLET R0F, R, 0Trims/extends two lines to a sharp corner

Common mistakes

  • TRIM deletes the whole line.

    In Quick mode, a segment with no crossing edge is deleted. Undo and check the edge really crosses.

  • EXTEND says the object does not intersect.

    Turn on the Edge › Extend option, or extend to an object that actually lies in the path.

Exercise

Clean up wall intersections

  1. Draw a 6000 × 4000 rectangle with LINE and a vertical partition line that overshoots top and bottom.
  2. Trim the overshoots.
  3. Draw a horizontal line that stops short of both walls, and extend it to meet them.
  4. Use Shift inside TRIM to extend another short line.

You should end up with: Clean intersections with no overlapping lines.

Checklist

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Lesson quiz

1 / 4

In Quick mode, which objects act as cutting edges?

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Free, independent learning material written for KitWren. AutoCAD and AutoCAD LT are registered trademarks of Autodesk, Inc. KitWren is not affiliated with, sponsored or endorsed by Autodesk. We never provide software downloads, licence keys or cracks — use the official sources.