To Subtract From Linework Objects

Subtract a selected part from linework or from a block containing linework without having to redraw any of the remaining components. The part to be subtracted can contain or be delineated by lines, polylines (closed or open), arcs, circles, text, or hatches. If the subtraction removes part of a closed polyline, the polyline is recreated as closed. If the subtraction bisects a closed polyline, both parts are recreated as separate closed polylines. However, when the subtraction bisects a hatch, the hatch remains a single linework entity that you can select by clicking either part.

Note: Anything subtracted by this operation is actually deleted from the drawing. If you want to hide linework from view, you may want to use the Obscure command instead.
  1. If it does not already exist, draw the linework that delineates what you want to subtract.
  2. Select the linework or object from which to subtract the delineated part.
  3. Right-click and click AEC Modify ToolsSubtract.
  4. Select the linework delineating the part you want to subtract. Press Enter.
  5. Press Enter to retain the selected linework. Enter y (Yes) to erase it.

Subtracting part of a block