This is a plugin, I've been trying to figure out for a few months. Just got the "Automatic Sketchup" book last week, which helped alot. Like the name saids, deletes all interior faces. Just select and use right click context menu. Look in submenu [kyyu].
Copyright(C) 2010, kyyu
All Rights Reserved
Name: Delete Interior Faces
Version: 1.0
SU Version: 7.0
Date: 05-04-2010
Description: This plugin deletes all Interior Faces of a part(s)
Usage: Select the parts and right click context menu ( [kyyu]/Delete Interior Faces )
History:
1.0 (05-04-2010) - first version
Delete Interior Faces_1.png
Delete Interior Faces_2.png
ky_Delete_Interior_Faces.rb
Delete_Hole_testing.skp
-Kwok