alt belt and pulley

[Danny]

whats up all. just picked up an alternator. I have 2 questions. One being the way that the belt rests in the pulley. Does the belt just lie on top of the pulley or does it actually sit in it. And is the pulley one piece or is it made up of numerous pieces. The pulley that was on my old alternator, it had been switched out before, was actually 4 pieces. And of course upon disassembling it, i didnt stop to look at how the parts were configured. Im tryin to figure out if the p.o. rigged it together or if this is how the pulleys are. 2 belts down and about to pull my alt out again to redo the pulley assembly so that the space is a bit wider, so the belt fits into the pulley.  tia
                   danny