Well-known Boston Marathon race director, Dave McGillivray, who also founded DMSE Sports, once got locked in a port-a-potty 20 minutes before the start of the Boston Marathon. Everyone was waiting for him and he was stuck. “And then I dropped my two-way radio into the unit,” he said, while he was trying to get out.

The lesson here: If you’re going to lock a port-a-potty and keep it hidden just for race staff, don’t use it and leave the lock sitting outside where someone might accidentally re-lock it with you in it.

Every race director has port-a-potty stories—like that time someone lit a bank of them on fire the night before the event, another McGillivray classic. That’s because port-a-potties, port-a-johns, portable toi...