As I'm trying to learn Hammer, I've been snooping around the maps of other's gleaning techniques and such. Now I'm confused on the hows and whys of No Draw and Invisible tool textures. Can anybody help me out on these two and correct their application?

Cheers

http://developer.valvesoftware.com/wiki/Tool_textures

A good tip I use is to make the map out of no draw, makes optimising much easier in the future as you go hunting for textured faces that arent seen.

As for other unseen ones things like trigger and player clip are self explanitory but Furyo has given you everything you need on that link