First, you need to read the General Games Section rules, which all apply here. Here are the rules specific to the Valve Games and Mods section:

This is NOT the place to post GMOD related threads. If you need help with GMOD, click here to be redirected to where you SHOULD be posting.
This is NOT a Steam Support section. If you have any questions or problems with Steam, use their official forums or Steam Support for assistance.
If you're having problems with a Valve Game or Mod, DON'T make a thread here about it. Use the appropriate megathread if it exists, or use the Steam Users' Forum section or official forum for that game/mod.
This isn't the place to recruit for your mod, or to ask people to help you with your modifications. If your mod isn't working, don't make a thread here about it.

If you don't follow these rules while making a thread, it will be locked, and you may be banned. This is your only warning.

Report threads and posters that you see breaking these rules.

PM a moderator if you have a rule you'd like added to the list.