AutoCAD Double Line LISP: Parallel Walls with Clean Corners

Draws two parallel polylines at a set width through the points you pick, with clean mitred corners.

This AutoCAD double line LISP adds the DOUBLELINE command, which draws two parallel lines at a width you choose along a path of points you pick. It is meant for anything shown as a double line on a plan: walls, ducts, cable trays, roads.

Corners come out mitred, so the inner and outer lines meet cleanly and you don't have to fix them with TRIM or FILLET afterward. A justification option sets whether your picked points run along the center, the left edge or the right edge of the double line, where left and right follow the drawing direction.

AutoCAD's built-in MLINE also draws double lines, but it creates a single multiline object that you edit with MLEDIT or explode first. DOUBLELINE instead leaves two ordinary LWPOLYLINE objects on the current layer, so you can edit them right away with OFFSET, TRIM, STRETCH and the rest of your usual commands.

How to use it

1. Load doubleline.lsp with APPLOAD and type DOUBLELINE at the command line.
2. Enter the width, or press Enter to accept the last value shown in brackets.
3. Choose the justification: Center, Left or Right.
4. Pick the start point and the following points; use Undo to drop a point you picked by mistake.
5. Press Enter to finish an open path, or choose Close to close it into a loop.

Notes and tips

• It draws straight segments only; arcs are not supported.
• The ends of an open path are left open; add short closing lines yourself if you need them.
• Width and justification are remembered for the session; the defaults are 10 and Center.
• The polylines are 2D and go on the current layer. Tools that work on LINE objects only, such as WALLGAP, need them exploded first.

Frequently asked questions