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Reference

JOIN in AutoCAD

How AutoCAD's JOIN (J) works: lines and arcs that meet into a polyline, collinear lines into one, arcs into a circle, curves into a spline. Try it free online.

JOIN makes one object of several. Select them, as many as you like, and press Enter: lines and arcs that meet end to end become one polyline, joined to a polyline among them if there is one; lines on one straight line become one line, over any gap; arcs of one circle become one arc, and when they close, JOIN asks whether to make it a circle, Yes by default, or keep it as an arc with No. Elliptical arcs of one ellipse become one arc, and a spline or an elliptical arc among curves that meet makes a spline. It then says what it made, and how many objects it left out. A polyline joins only by its ends, and a closed one joins nothing. The join is one step that Undo takes back.

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.

Three lines joined into one polyline, which one pick of OFFSET then follows whole.
  1. Command: JOIN
  2. Select source object or multiple objects to join at once: 1 found
  3. Select objects to join: 1 found, 2 total
  4. Select objects to join: 1 found, 3 total
  5. Select objects to join:
  6. 3 objects converted to 1 polyline
  7. Command: OFFSET
  8. Current settings: Erase source=No Layer=Source OFFSETGAPTYPE=0
  9. Specify offset distance or [Through/Erase/Layer] <Through>: 8
  10. Select object to offset or [Exit/Undo] <Exit>:
  11. Specify point on side to offset or [Exit/Multiple/Undo] <Exit>:
  12. Select object to offset or [Exit/Undo] <Exit>:
Three lines joined into one polyline, which one pick of OFFSET then follows whole.

Options

cLose (L)

When an elliptical arc is the source, picked alone: makes its ellipse whole.

What it does not do yet

AutoCAD's own step when a single line, arc or polyline is the source, picked alone (Select lines to join to source:): here it joins nothing. A closed object picked alone, which AutoCAD asks again for. Helixes, objects in a tilted plane or upside down, and lines that do not lie in one plane, which AutoCAD joins into a 3D polyline or flattens into a polyline.

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

Questions

What is the shortcut for JOIN in AutoCAD?

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

How do I join lines into a polyline in AutoCAD?

Run JOIN, select the lines, with a window if you like, and press Enter: those that meet end to end become one polyline.

Why does JOIN not work?

The objects must meet exactly, end to end and in one plane: a gap or a crossing leaves them out, and JOIN says how many it discarded. Only collinear lines, arcs of one circle and arcs of one ellipse are joined over a gap. A closed polyline joins nothing.

How do I join arcs into a circle?

Select arcs of one circle that cover it all, and press Enter: JOIN asks whether to convert them to a circle, and Yes, the default, does.

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