.Map :: MoHAA Mapping

In radiant,

How do you make a brush invisible.

How do you make a brush not solid ............ ?

One way is to texture the brush with common "nodraw". Some textures are already "non solid" (key S for the surface inspector). But, you can also make the brush a "script_object" entity (key N for the entity window) and select "not_solid" as one of its properties.