If you've built complicated elevators (lifts, to those across the pond from us Americans), you've almost certainly run across a Marathon engine limitation which can make it impossible to use the action key to trigger the elevator control (punching or projectiles are all it recognizes). This happens because the active area for a switch comes at some fixed percentage of the floor-to-ceiling height, which may or may not correspond to where you've got a switch. HAS has released a quick demo map showing a rather elegant way around this problem. (If you don't understand my wording of the problem, download the file. It's pretty small. If you're making maps, it could help you make more elegant ones.)