Collision mesh for a hole is not working

[DwarfOverlord]

Hi,

I've made a model of a hole in a wall for my csgo map in blender, however I can't get the collision mesh to work right. I used knife tool to carve the hole in the middle and then extruded the rest of the face to make it seem like a hole in a wall.
Here's the collision mesh as it appears in hammer: [IMG]https://dl.dropboxusercontent.com/s/7dzq1g52bb4npcq/eg.PNG[/IMG]
Here's what the model looks like in blender: [IMG]https://dl.dropboxusercontent.com/s/zyut39qgxh6nyzc/eg2.PNG[/IMG]
The dots I've circled seem to be what is making the collision all borked up. It's as if the face is still there, although it isn't. How do I get rid of this so that a player can crouch through this hole instead of being blocked by an invisible face?

[Deunan]

Yeah, a collision mesh can be made from up to 32 pieces, but each of the pieces has to be convex. Your mesh seems like a single piece which is convex.

Also you need to compile with the $concave flag in the QC.

Would probably be better for you to make the wall itself have no collision, and build a dirty collision around it with $nodraw brushes in hammer.