ABSTRACT OF THE DISCLOSURE An apparatus that facilitates the manufacture of wooden stairs of the type having treads and risers extending between and affixed to side housings or stringers. The apparatus provides multiple, parallel guides for the router used to cut the grooves in the stringers into which are fitted the treads and risers. By using a parallelogram construction for the multiple guides, the apparatus can be quickly adjusted and set to produce almost any size of stairs. An index bar used with the apparatus allows the apparatus to be quickly set for the particular stairs desired so that the grooves for both the treads and risers can be cut quickly and accurately in the stringers. The router is moved along each of the parallel guides to cut the grooves for all of the treads, and then the apparatus is quickly and easily reset and locked into position to set the guides for cutting of the grooves for the risers.