A stairway can be constructed by using movable treadriser supports placed along a stairway stringer and the supports can be moved as a group or individually to accommodate a stairway slope of any desired degree. The friction device interacts with said rope to retard the movement of the controller along the rope. The linkage is engaged with the control lever, the hydraulic dump actuators, and the brake actuators of the first and second hydrostatic transmissions.