Find 3D Solid Interference (Tip #2064) by Andrzej Gumula is a clever routine that exploits the powerful Visual LISP object manipulators. This function locates the interference between solid objects and creates an interference object for you to view. For those looking to do advanced 3D work inside AutoCAD, this is a nice utility. Load the LSP code and type FIN to activate. Select the 3D solid objects to check, and the rest is automatic except for a slight pause to let you step through viewing the interference objects created. Harry's first reaction was this tip is really cool. And that was before he ran the code. Thanks to frequent tipster Andrzej for this gem!