When TRIM asks you to select cutting edges, it will accept and highlight
objects within blocks or within external references. However, it will only
trim using edges that are within blocks. Edges that are within external
references are ignored, even though there's no error message about "not a
valid edge". EXTEND behaves the same way.
Lines and polylines can be grip edited so that they stop at edges defined by
objects within external references, so it appears that AutoCAD can, in fact,
find the intersections involved.
Is this intentional? Why would TRIM and EXTEND "fake out" the user by
allowing him to select edges that then don't get used? Is there some system
variable or setting I'm missing?
Thanks
Michael Evans