And when there is not a tower nearby, you, uhh... find a way. My buddy was flying into one of the many uncontrolled airports in NorCal, and there was a guy in a single-engine retractable gear circling the airport. When Buddy made his downwind call, the Guy radioed "Hey I'm not getting any indication whether my gear is down or not, can you fly by me and tell me if it's down?" It was down, so Guy ended up attempting the landing with a bit more confidence than he started out with.