A stairway is comprised of various components that fit together to allow access from one floor of a building to another. The horizontal boards, which are the pieces actually stepped on, are called the treads. These should be sufficiently deep to enable users to place their feet down comfortably without slipping. The vertical boards that meet each tread at right angles and that raise the stairway are called the risers. These can vary in height depending on architectural requirements. On many stairways, the treat just out a small amount over the riser and this feature is known as a noising. The treads and risers are supported on an inclined structure called a stringer that runs flush with the sides of the staircase and presents a diagonal saw-toothed pattern when viewed from the side.
For safety, a stairway usually has a handrail on one side resting on vertical supports called balusters. Balusters and handrails together are known as banisters, and these are firmly supported at the bottom and top of the stairs by heavy posts.
Whereas these features are common to most stairway types, the actual layout of the stairway will vary depending on space and aesthetic considerations. If the stairway turns back on itself a total of 180 degrees, the landing, which is the flat area at the top of the stairs, will be twice the width of the stairs. If the stairs turn at right angles, the landing will be the width of the stairs. Perhaps the most elegant layout is called a spiral stairway. This structure usually rises around a central vertical post to which tapered treats are attached at their narrow end.