As you can see this STool spawns various doors, which can be opened and closed using the numpad. You can also set an auto-close delay, e.g. when you open it closes after 5 seconds.

This addon includes the following doors:

Combine door
Tall combine door
Large combine door
Two types of wooden door
Blast door
Elevator gate

I take no credit for this, I just re-packaged it as an addon for ease of use.

For all you MingeBags out there, here is where you put it: C:/ProgramFiles/Steam/SteamApps/<YourSteamName>/GarrysMod/GarrysMod/Addons