From StrategyWiki, the free strategy guide and walkthrough wiki

Getting around in MOTAS is pretty easy, all you need to do is click on different things. For example, you can click on a door (providing it's unlocked) and then click on the opening to get to another room. Or you can click on a hole in the ceiling or floor to drop down or climb up to the next floor. This is, of course, providing there's a ladder or a rope leading up or down the hole.