This command tags polylines with a description so that Triangulate & Contour can identify these polylines as hard breaklines. The tag is invisible and doesn't change the polyline. Triangulate & Contour will not smooth the contours as they crosses these hard breaklines. For example you could tag 3D polylines that represent a wall or a curb so that the contours go straight across without smoothing curves.
Select hard breaklines.
Select objects: select polylines
Pulldown Menu Location: 3D Data > Hard Breaklines
Keyboard Command: hardbrk
Prerequisite: Polylines
File Name: \lsp\hardbrk.lsp