A sliding door is a type of door which opens horizontally by sliding, usually parallel to a wall. There are several types of sliding doors. Sliding doors can be mounted either on top of a track below or be suspended from a track above, while some types ‘disappear’ in a wall when slid open. Because all the weight of the door is suspended on the rollers attached to the door, weight is a major consideration. If the door is too heavy, it will be difficult to open and may bend off the track.