Many shelf-pin hole jigs consist of a long board with a line of holes drilled into them: sometimes costly to buy, often time-consuming to make, and always a pain to store. But this router subbase solves all of those problems.

The shop-made subbase (I made mine out of 1/2" medium-density fiberboard) has a 1/4"-20 bolt that acts as an index pin. For shelf-pin holes 1" apart, drill a 1/2" counterbore 3/16" deep on the face of the base, centered 1" from the center of the router collet; then drill a 1/4" hole completely through the subbase centered in the counterbore. Countersink the hole on the back of the subbase. Now, insert a 3/4" long 1/4"-20 flathead bolt, and secure it with a nut inserted in the counterbore. Mount the subbase to your router and install a 1/4" straight bit, set for a 1/4" plunge depth.

To use the jig, clamp a straightedge to the shelf side to position the bit the desired distance away from the edge of the case. With the base firmly against the straightedge, position the bolt against the end of the case side and plunge the first hole. Lift and slide the router over, positioning the bolt in the first hole. Keeping the router firmly against the straightedge, plunge the second hole. Repeat the procedure, using each preceding hole to index the router for the next.
—Bas Pluim, Cary, N.C.