How to Create door with breakable glass in Left 4 Dead 2
L4D2, or Left 4 Dead 2 to the uninitiated, is a popular 1st person shooter from Valve with a very good, but complex, level editor. This video will teach you how to do one cool thing in the editor: create door with breakable glass panels that will move properly with the door. Don't scream at the windows in your door for not moving anymore; show them how.
Text tutorial here.