How to connect two lines together in AutoCAD?

ByCADbrief Staff

How to connect two lines together in AutoCAD

Short Answer

To connect two lines together in AutoCAD, the most common professional method is FILLET with the radius set to 0, which trims or extends both lines until they meet at a clean corner. This is fast, precise, and widely used in drafting workflows. It only works correctly when the line endpoints can logically intersect.

What You Need to Know Before

Warning: If the lines are on locked layers, inside a block, or are not true LINE objects, the connection may fail or affect the wrong geometry. A very common issue is trying to connect lines that are actually separate polyline segments or have a large gap with no possible intersection.

How to Connect Two Lines in AutoCAD

  • Command: FILLET

  • Shortcut: F

  • Quick Steps:

    1. On the Ribbon, go to Home > Modify panel > Fillet, or type F and press Enter.
    2. Type R, press Enter, then enter 0 to set the fillet radius to zero.
    3. Click the first line, then click the second line; AutoCAD will trim or extend them so they connect.

Variables & Settings

  • Key Setting: Trim option in the FILLET command

  • Expert Setting: Set Trim to Yes so AutoCAD automatically trims or extends the selected lines to their intersection. If Trim is set to No, the lines may not visually join as expected.

Why it Fails

  • Cause 1 (Geometry): The two lines are parallel or positioned so they cannot intersect, even if extended.
  • Cause 2 (Layers/Locks): One or both lines are on a locked layer, in an external reference, or inside a block you are not editing.
  • Cause 3 (Command/Logic): FILLET radius is not set to 0, or Trim is disabled, so AutoCAD creates a rounded corner or does not produce the intended connection.

Quick Fix & Best Practice

  • Quick Fix: Run FILLET, set Radius = 0, confirm Trim = Yes, and select the two lines again.
  • Manager’s Verdict: Use FILLET with zero radius for everyday 2D drafting because it is the fastest standard method. Avoid it when the objects should remain untrimmed or when you need to preserve exact original endpoints for coordination.

FAQ

Can I connect lines without trimming them?

Yes, use FILLET with Trim set to No, but the lines may not appear physically joined.

What if the objects are polylines instead of lines?

FILLET still works in many cases, but editing the polyline with grips or PEDIT may be better.

Can I connect more than two lines at once?

Not directly with standard FILLET picking; connect them pair by pair or use PEDIT if they should become one polyline.

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