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Reference

EXTEND in AutoCAD

How AutoCAD's EXTEND (EX) works, prompt by prompt: Quick and Standard modes, boundary edges, fence, crossing and Edge, and Shift to trim. Try it free online.

EXTEND lengthens an object until it meets another: you pick it near the end that should grow, and that end runs on to the nearest edge in its way. It extends lines, arcs, elliptical arcs, open polylines (along their end segment, straight or round its arc), 3D polylines and open splines. It starts in Quick mode, as AutoCAD's does: every object is a boundary. Holding Shift as you pick trims instead, as TRIM does. Each pick is one step that Undo takes back; Enter ends the command.

At the command line

The engine draws it and writes its history as you would type it: the prompts in AutoCAD 2027's order, with the same option letters.

Two lines grown to the line across their path: each picked once near the end that grows, in Quick mode.
  1. Command: EXTEND
  2. Current settings: Projection=UCS, Edge=None, Mode=Quick
  3. Select object to extend or shift-select to trim or [Boundary edges/Crossing/mOde]:
  4. Select object to extend or shift-select to trim or [Boundary edges/Crossing/mOde/Undo]:
  5. Select object to extend or shift-select to trim or [Boundary edges/Crossing/mOde/Undo]:
Two lines grown to the line across their path: each picked once near the end that grows, in Quick mode.

Options

Boundary edges (B)

Chooses which objects bound: select them, or press Enter to take every object. From then on only those bound, whatever the mode, until the command ends.

Fence (F)

Asks for the points of a line, as many as you like until Enter: every object it crosses is extended from the end nearer where the fence crosses it, in one step. Standard mode lists it; Quick mode takes it too.

Crossing (C)

Asks for the two corners of a window: every object its outline crosses is extended, in one step.

mOde (O)

Switches between Quick and Standard. In Standard mode EXTEND first asks for the boundary edges (Enter takes them all) and lists Fence and Edge. The mode is EXTEND's and TRIM's both, and lasts the session.

Edge (E)

Standard mode only. With Extend, an object also stops where a boundary would be if it ran on — a line both ways, an arc round its circle — so a line can grow to one that falls short of its path; No extend is the default.

Undo (U)

Listed once the prompt has had an answer — a pick, a fence, a window: takes back the last extension, and with nothing left to take back says so.

What it does not do yet

Project: AutoCAD's projection option (None, Ucs, View) is not offered, and everything is worked out projected on the UCS's XY plane, which is AutoCAD's default, Ucs. A fence cannot be dragged with the cursor yet, only picked point by point. The mode and Edge's choice last the session, where AutoCAD keeps them from one session to the next. An object at an angle to the UCS, a spline aside, neither bounds nor is extended, and a polyline smoothed by PEDIT's Fit is refused, where AutoCAD grows its last arc.

What it does and still lacks, in detail (in English)

Questions

What is the shortcut for EXTEND in AutoCAD?

EX, then Enter or Space. The full name works too, and _EXTEND in any language of AutoCAD.

Why does EXTEND say there is no edge?

Because nothing lies across the path that end would follow. A line says No edge in that direction. when its other end would reach an edge, and a line or an arc Path does not intersect with the bounding edge. otherwise; a polyline or a spline says Object does not intersect an edge.. Pick nearer the other end, or in Standard mode choose Edge and Extend to let a boundary that falls short count as if it ran on. A circle, a closed polyline, a whole ellipse, text or a hatch cannot be extended at all: Cannot EXTEND this object.

How do I extend several lines at once?

Pick on an empty spot and pick a second point: every object that fence crosses grows from its nearer end, in one step. Or choose Crossing and draw a window over the ends to extend.

How do I trim with EXTEND?

Hold Shift as you pick: the piece is trimmed back to the nearest crossings, as TRIM would, and an object that nothing crosses is deleted. The next pick without Shift extends again.

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