Straight-run flights of stairs can be connected by flat rectangular landings or by winders.
Winders are staircase elements consisting of steps that fit together and curve round to create a connecting bend between two straight-run flights of stairs. The tread of each winder step has a wide end and a narrow end which allows for the curve to be constructed.
Thus winders may be used in combination with straight flights of stairs to turn the direction of the staircase. This allows for a large number of permutations.
[see straight staircase, L-shaped staircase and U-shaped staircase}