Valve Source SDK hammer help. Thread

I been learning how to make maps for about 4 days now and there is Three things I still do not know how to do, so can someone help me?
The first thing is, How do I make holes in wall? I tried using the clipping tool but I'm wondering if there is a better way.
The second thing is, how do I make multiple pieces of a wall into one hole thing? after using the clipper tool to make the hole I wanted to make the pieces outside into one piece again. Any Idea how I can?
And the third and last thing is, How do I know how big to make a hole for a door to fit?
That's about it if you have any questions about my questions please ask.

Assuming you have a wall that you want to make the door out of, generally you would 'cut' across the level you want the top of the door to be, then on the lower piece of the 2 new brushes you have created, you will want to 'cut' the width of the door.

The lazy way to do this is to take a brush that represents the size of the entryway you desire, put it into the desired position and use the 'carve' tool. This is very lazy, and the cuts made by carve will be less than optimal and won't allow for proper door placements across the entire brush generally. No one will every suggest using carve, but sometimes i do feel lazy when I need to put the same hole across the same wall 10 times. This is about the only scenario that carve has a chance of not screwing your map up, and it still can, as it cuts any brush in it's way. If you accidently make your door brush too long, or it is on the edge of another brush, it''ll carve it as well.

If you need to check the size of your doors, you can either find a texture with a door on it, or simply use one of your 'info_' entities to guage size. I think player_info has a place holder entity that is the basic size of a player model, and is quite useful in that regard. That or it is player_start.

The other answer: 1 unit is roughly 1 inch. Players are roughly 64 inches tall, or 5'4'' tall. Stairs have a rise of 4 units, in general, but the run really depends upon your own personal tastes. I like to do a rise of 4 units and a run of 8 units in a house type of building, while keeping it rise 4 run 4 in more industrial settings.

If you have any other questions, just consult the dev wiki or Interlopers. They have many great guides there.

Ok well now I need one more question awnsered, how to I make multiple peices of something into one whole piece? like if I cut something up with my clipping tool how can I make it one again (without just undoing)

well you cant make it into a single solid really, but you can group them together so you can move it around as a whole.