3 Questions
Okay so, in my map I use a tractor beam and then above I have a grate. I want the grate to stop both the player AND objects (cubes etc) but still allow the tractor beam to pass through, when its turned on.
Previous solutions I have tried, but don't work properly are:
The grate being a func_brush with Solidity set to never solid and with a player clip box above it. This stops the playing falling through, and allows the tractor beam but DOES NOT stop boxes falling through the gate.
The second question is when going through portals, you can sometimes see through doors. Its a visual glitch that flickers, but I would like to stop that happening if possible.
Third question is regarding the tractor beam prefab, I have set one down in my map, and I have Started Disabled set to Yes, and start enabled set to No. However the beam is still enabled on map load, what gives? I might add a command OnMapLoad in logic_auto to turn it off, but having to do with that multiple tractor beams would be annoying, is there any easy fix? 
Thanks
Check out my Portal 2 map, Entrapment!
http://forums.thinking.withportals.com/community-releases/entrapment-1-1-1-t2323.html
For the first question: Add a func_clip_vphysics to your clip. That should stop all physics objects from going through without stopping the beam. Another option is to use hard light bridges instead of a grate.