Day 12
Editing
60 XP

JOIN

Combine separate segments into one polyline.

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Learning objective

By the end of this lesson you can merge connected line segments into a single polyline using the JOIN command.

What JOIN is

JOIN combines two or more collinear or end-touching objects into a single object — usually a polyline. It is the inverse of EXPLODE.

Why and when you use it

Many commands (HATCH, OFFSET, EXTRUDE) need a single closed object, not a collection of line segments. JOIN gives you that single object.

Where to find it in the AutoCAD interface

Ribbon
Home tab → Modify panel → Join (in the expanded panel).
Menu
Modify menu → Join.
Command line
Type JOIN and press Enter.
Alias / shortcut
J (then Enter).

Key vocabulary

Polyline
A connected sequence of line or arc segments that behave as one object.
Source object
The first object picked at the prompt — others are joined to it.
Collinear
Lying on the same straight line.

Before you start

  • Draw or have several line segments whose endpoints actually touch.
  • Turn OSNAP on (F3) so endpoints meet exactly — JOIN needs precise contact.
  • Press Esc twice to clear any stale selection.

Step-by-step instructions

  1. 1
    Start the JOIN command
  2. 2
    Select the first segment
  3. 3
    Select the remaining segments
  4. 4
    Verify the result

Common mistakes & fixes

  • JOIN reports '0 segments joined'.
    Fix: Endpoints don't touch exactly. Turn on OSNAP and re-snap the corners first.
  • Joining lines that don't share a single shape.
    Fix: JOIN needs end-to-end contact. Use BLOCK to group disconnected geometry instead.
  • Trying to JOIN a hatch or block.
    Fix: JOIN only works on linework — explode complex objects first if appropriate.

Troubleshooting

Endpoints look connected but JOIN fails.Show
Cause: There's a sub-pixel gap.
Fix: Snap each endpoint with OSNAP, or use PEDIT → Join with a tiny fuzz distance.
Result is still many objects.Show
Cause: Some segments weren't selected.
Fix: Window-select all segments at once and rerun JOIN.

Practice exercise

Four lines → one polyline
  1. Draw four LINE segments forming a closed square (snap each endpoint).
  2. Type J, Enter.
  3. Select all four lines, press Enter.
  4. Click any edge — the whole square should highlight as one object.
Success looks like: Four separate lines become one closed polyline you can HATCH, OFFSET or EXTRUDE.

Pro tips & related commands

Pro tips
  • JOIN can merge collinear lines into one longer line, even with a gap.
  • Use PEDIT → Join with a fuzz distance for messy imports where endpoints are nearly touching.
  • Run OVERKILL to delete duplicate overlapping segments before JOIN.
Related commands
  • PEDIT(PE)
    Edit a polyline — also has a Join option with fuzz tolerance.
  • EXPLODE(X)
    Break a polyline back into individual segments — the inverse of JOIN.
  • OVERKILL
    Delete duplicate or overlapping geometry before joining.
Lesson quiz
0/2 correct

Score at least 2/2 to unlock lesson completion.

1. JOIN fails with '0 joined'. Most likely cause?
2. After JOIN succeeds, the result is…

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BLOCKSEXTRUDE

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