The main structural beam supporting a staircase. Sometimes called a stringer. If the guardrail is made up of two pieces, the bottom piece to which the balusters are attached is the sub rail. The measure of the angle formed by the relationship of rise to run on a staircase. The upper surface of a step in a stair.
Tread rise The vertical measurement from the top of one tread to the top of the next tread in line.
Tread run The horizontal distance measured from the front of one tread to the front of the next tread above or below it. Wainscot Mouldings which stops part way up a wall, usually capped by a heavy moulding called chairrail. Any staircase which changes direction while walking on individual treads which are tapered along their run.