More than 30 years ago, I worked as a sales person for a very large furniture chain in Saginaw, Mich. At this mega store, we had 25 sales people on staff, often all at the same time. With that many people waiting on prospective buyers, it was necessary to have an up system—a rotating schedule dictating who would get to talk to the next customer that walked in the door.
The system was simple: when you got to the store, you put your name on the list (first come first serve). So, as you might guess, your wages could be greatly influenced by how early you got to the store each morning. If you were lazy and got there just on time, you could be last on that list, which meant on slow days you might not even get an up.