Abstract: The disclosure relates to a joint fastening two slats on boards of wood perpendicularly to one another and the method and apparatus for making that joint. Abutting ends of wood bevelled at 45.degree. angles to one another are locked in place by a bevelled wood spline which fits into dovetail grooves cut by a router through the slates. The jig for cutting the dovetail grooves includes a slotted template and a clamping apparatus for holding the wood at an angle to the template. A router is guided by the template to make the appropriate grooves which receive the spline. Another portion of the jig includes a slotted template which guides the router for bevelling the spline.