Here's a question that isn't nearly as urgent as the seat belt one was. Is the light on the back of the cab a high-mount stop light or just a dome light for the bed?

Mine has been replaced with.. I think it's electrical tape. I'm not in a hurry to fix it, but want to eventually because I imagine the tape is not going to keep water out forever. Just so I know what to look for, what am I looking for?