I am working on an SP map. Though I made a light and I clipped off a chunk to make it into a floor light. Kinda like this ( II\ ). The thing is in game the player can walk through the light. I think I have to change a property of it or something, please help with a step by step process.
Do you have any nonsolid shaders on any surface of the brush? These would be things like nodraw, caulk_nonsolid, water, or anything ending in _noclip. Some of the metal shaders actually have _noclip, and make brushes they're put onto nonsolid!