
The clipping tool allows you to clip walls and ultimately make them not rectangles at all as how they were spawned. Clipping Tool- This tool is one of the two coolest tools.It takes the same overlay features (texture application features) and applies them to the selected surface. Apply Overlay Tool- I have never used this tool so its *obviously* not very important.To use it, click on the selection tool and then click on the Apply Decals tool, then while looking at a wall you want to apply a decal to, click on it in the 3D render window and it should pop up on that wall. Decals help 'beautify' a map (posters, spray paint, etc). Apply Decals Tool-This tool is for applying decals, which is semi-important.Apply Texture Tool- Self-explanatory- it just changes anything you've selected with whatever texture you currently have in your upper right texture menu.The 'Displacement' tool is used for making hills and such. You can also replace textures, rotate, and scale them.

Texture Application Tool- This tool is useful because it lets you target a texture on a surface rather than the entire object's texture.It is used to create the 'hull' of the map. Block Creation Tool- The BC Tool is the most important tool in Hammer, as it is what allows you to create your maps.

Most commonly used are info_player_start, light, light_environment, prop_physics, etc. To access the list of entities, when you click on the Entity Tool, a list on the lower right side of your Hammer should say "Categories: Entities" click on the drop down menu below that and you'll find a list of entities to spawn.
