Both types slide vertically in tracks on each side of the door. If the segments are narrow, they may slide in the track directly. If the segments are wider, each segment may have wheels that roll in the track, as in Figure 1. The only difference between the two is that the roll-up door is stored on a spool at the top of the door, while the overhead door slides on its track to an overhead position. The roll-up door has narrower segments, and it takes up less ceiling space.