A stair tread is the horizontal portion of a set of stairs on which a person walks. It can be composed of various materials such as wood, metal, plastic, or tile. In residential settings, treads can be covered in carpeting. Stair treads can come in non-slip varieties, particularly in commercial or industrial locations. The depth of the tread, or the distance from the front of the tread to the back, is part of the run calculation in building steps. The size of each tread can affect both the comfort and safety of climbing the stairs. Treads that are too shallow dont give enough room to safely plant the foot while going up or down the stairs, while an overly deep tread can make it tough to take just one step on each tread. There are different styles of treads, including mid-flight treads, feature or starting treads, and winder treads.