A "Floating Fort" is basicly a group of objects (typically containers, crates, and palettes) that have been placed on top of floating teleporters, giving players that are inside good cover, and a good angle. They're generally used in infection games, with the humans defending the fort from the attacking zombies. You can make one in Forge, by following these steps:
~Place an object on the ground
~Put a teleporter (a reciever node works best) on top of the previously mentioned object
~Delete the object after the teleporter has settled in one position
~Place another object, like an empty container, for instance, on the top of the teleporter
~If you want to, you can put any weapons, vehicles, equipment, or even a grav lift on or in the container