Slipgates in Quake are devices built by the humans of Earth before they were stolen and used by Quake as a way of teleporting onto Earth. They were made to transport humans and cargo from one place to another instantaneously. As they were possessed by Shub-Niggurath to transport her spawn of daemonic aliens from the other dimension's, the gateway was still open when Ranger went through. Other than their creators, they are exactly the same as a Teleporter, besides the fact that there is a slipgate on the floor where you start. Also they are only used to enter and exit a Base level. In the level after the Base level there is an entrance Slipgate to keep continuity of the levels. In deathmatch games, the Slipgate has a larger border around it so the player does not accidentally step into it.