curved stairs: no mystery just simple math | thisiscarpentry i have a straight stair case from the second floor to the first floor. the bottom two steps are carved in pie shaped treads with square corners by the wall. they are not the same size. how do i mark the radius so i can put a trim piece on the tread to accept my laminate wood which is 48 inches long. the treads are 52-521/2 inches wide.