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BARB LISP: Draw Leader Arrows Sized from DIMASZ

Arrows drawn by hand end up whatever size the person drawing them guessed at, and they are wrong again the moment the sheet scale changes. BARB draws leader-style arrows as plain polylines, sized automatically from the drawing’s own dimension settings.

What Barb does

The arrowhead length is DIMASZ multiplied by DIMSCALE — exactly the size AutoCAD would use for a real dimension arrowhead at the current annotation scale. That is the whole point: the arrows match the dimensions already on the sheet without anyone having to remember what the scale is, and they come out right the moment DIMSCALE changes.

Three commands. BARB draws a standard arrow with the head one third of DIMASZ wide. FATBARB draws a heavy arrow with the head a full DIMASZ wide, for when the arrow needs to carry across a busy drawing. CURVEBARB uses the standard head but draws the tail as a spline rather than straight segments, which is useful for curving a note around existing geometry.

All three prompt continuously for further points, so one command draws a multi-segment leader. Press Enter to finish.

How to use it

  1. Load the routine with APPLOAD, or put it on your support file search path.
  2. Type BARB, FATBARB or CURVEBARB.
  3. Pick the arrow point — the end the head goes on.
  4. Pick the next point, and keep picking for a multi-segment leader.
  5. Press Enter to finish.

How it works

The head is a tapered polyline segment. It starts at full width and tapers to nothing, which is what produces the solid triangular point — no separate solid, no block, no hatch. The tail that follows is drawn at zero width, so it reads as a thin leader line.

The result is therefore a single polyline. It can be edited with PEDIT, offset, trimmed, put on any layer, and it plots by the usual lineweight rules. There is nothing special about it that a future user has to know.

Because the size is taken from DIMASZ × DIMSCALE at the moment of drawing, an arrow drawn on a 1:100 sheet and an arrow drawn on a 1:50 detail both come out the right size on paper without any thought.

Notes and limits

  • The size is fixed when drawn. These are polylines, not annotative objects — changing DIMSCALE afterwards does not resize arrows already on the drawing. Draw them after the scale is settled.
  • Check DIMASZ and DIMSCALE are what you expect before starting. The arrows will faithfully match a wrong setting.
  • These are not leaders. There is no attached text and no leader behaviour — which is exactly why they are useful for pointing at things where a real leader would be over-specified.
  • CURVEBARB draws a spline tail, so it has spline editing behaviour rather than polyline vertices along that part.

Download and details

NameBarb — leader-style arrows as polylines, sized from the drawing
DownloadBarb.lsp — 10.8 KB, plain AutoLISP source. Downloads directly; no zip to unpack.
TypeAutoCAD AutoLISP routine
CommandsBARB, CURVEBARB, FATBARB
Requiresnothing beyond a CAD platform with AutoLISP.
Source size10.8 KB, 277 lines
Error handlingYes — a *error* handler restores every system variable it changed, on cancel as well as on error.
UndoThe whole operation is wrapped in a single undo group, so one U reverses all of it.
CompatibilityAutoCAD (any release with AutoLISP), BricsCAD, ZWCAD, GstarCAD, ProgeCAD and other IntelliCAD-based platforms. AutoCAD LT needs a LISP enabler. No .NET, no ObjectARX, no installer.
AuthorYZ, August 2026
LicenceFree to use, supplied “as is” with no warranty.

References