I'm trying to make a brush that is solid to portals on one side (also nonportalable) and allows portals through on the other.

Using a glass texture on one side and a metal grate texture on the other doesn't work.

Thanks..

is the player always in a certain position when he/she is allowed/not allowed to fire a portal through that brush?
Edit: if that is the case you could work with a func_no_portal_volume
Edit2: you can just have your material non-solid, add a clip texture to prevent people/items getting through, but enable portals. And if you're at the wrong side, activate the func_no_portal_volume, enable the func_no_portal_volume again if you are in the correct area

hope that helped

Ah, good idea, thanks..

I made it using a func_brush set to Never Solid with the grate/glass texture. Then I made a func_brush with a portal-blocking material set to Toggle/Don't Render, and a func_brush that allows portals through but blocks everything else (a grate) also set to Toggle/Don't Render.

The valid area has a trigger_multiple around it. When the player enters (OnStartTouchAll) enable the grate func_brush and disable the portal blocker. When the player exits (OnEndTouchAll), vice versa.