I did it a slightly different way that still works. I have a brush with a GRATE texture tied to func_illusionary with a clip brush, both grouped together and then tied to a func_door. Works nicely. I didn't check "passable", what does that do?
Let's say I have a fence. And there's a button on the other side of the fence to make it slide open. I want to be able to SHOOT through the fence to hit the button to make the fence slide open. Possible?