How to Build Modular Boxes

Download a larger version of the drawing and a materials list

To cut the tops and bottoms of the boxes, set the table saw fence to rip 12 inches wide (or use a portable circular saw and clamped straightedge for a guide).

Rip two 12-inch-wide lengths from the 4x8 plywood sheet. Then rip two pieces 10-1/2 inches wide (or to your measurements) from the remaining stock.

To support plywood during crosscutting, attach an auxiliary fence of 3/4-inch stock to the miter gauge with screws. Keep it about 1/8 inch from the fence to avoid binding.

Set the table saw blade and auxiliary fence to get a 12-inch-wide cut. Crosscut all the plywood lengths so you have 14 pieces 12x12 inches and 14 pieces 10-1/2x12 inches.

It's easy to go astray when assembling so many units, so build a clamping jig like the one shown in the following Steps 1-3 to help with assembly. Use it to hold the four sides square to each other while gluing and clamping. You can clamp the jig in just one corner, as shown in Step 3. If one corner is square, the opposite one is also square.

Sand with caution
When finishing these modular boxes, remember that hardwood plywood such as the birch plywood shown has a thin face veneer. If you sand too heavily in one area, it's possible to sand right through the veneer, an error that will show through the final finish. Always maintain a light hand with abrasives, even those with fine grit. Most plywood is fairly smooth to begin with, especially on the face side, so it doesn't take much sanding to prepare a surface for finishing.

To make a clamping jig, first clamp together (don't glue) a box top (B), bottom (B), and two sides (A). Be sure to assemble the pieces correctly. Measure the inside of the clamped box.

Cut scrap of 3/4-inch plywood to the box's inside dimensions, minus about 1 inch on each side. Bore 1-1/2-inch holes with a spade bit in a drill about 1 inch in from two adjacent edges. These holes will accommodate the clamp heads.

Assemble the top, bottom, and two sides with glue, then clamp the box, using the clamping jig to check for square. Make any needed adjustments before the glue dries.

After the glue has dried, remove all the clamps and drive 4d finishing nails into the corners to reinforce the assembly. Be sure the nails enter the wood squarely. A finishing option: Use screws and plugs.

Drive the heads of all the finishing nails below the surface of the wood with a nail set. Fill the holes with wood putty or filler and later sand them flush.

Fill all plywood edges, except those at the front of the box, with wood putty or filler.

Sand all filled edges smooth and lightly sand box surfaces. Remove sanding dust.

Apply a coat of primer to the box (except unfilled edges). Then sand lightly again.

Touch up any blemishes, then paint on one or two finish coats of semigloss enamel.

When the paint is dry, add ash veneer tape to the unfilled edges. Miter-cut the corners of the tape.