I recently came into possession of three old plywood boxes used by a professor to cart his books around. This is just a really simple way to maximize that potential new bookshelf space!

Step 1: Materials

Materials:

Three wooden boxes, two with lids
~9 feet of wooden dowels (I used 5/16")
~9 feet of pipe (I used 1/2" copper pipe. The dowels need to fit inside the pipe but don't have to be tight.)
8 metal braces w/screws
wood plugs
wood glue

Tools

drill (I used a 3/8" flat bit, a 1/4" auger bit, and a philips bit)
dremel (used for sanding off the ends of screws that breach the plywood and cutting the pipe)
belt sander (used for sanding the ends of the wooden dowel)
clamps
saw (used for cutting the dowels)

Step 2: Attach Metal Braces

See figure. The screws I used were a little longer than the plywood was thick. I used a dremel with a sanding drum to sand away the sharp point. The weight of the shelves should not rest on the metal braces - the dowels and pipe will support most of the weight.

You still have to add the dowels and metal pipes, so don't screw the metal braces on both sides of each set of boxes yet.

Step 3: Drill Holes and Prepare Dowels

I used three dowels for each set of shelves - one on the inside, where it is also supported by the metal brace, and two on the outside, 2" from each edge. The holes I drilled were just a hair smaller than the wooden dowels - this is actually a good thing! I used a belt sander to sand the edge of the dowels small enough to fit the holes. This way the shelves are supported by the edge of the dowel in addition to the metal pipe.

Of course, take care that the holes match up! In a perfect world all boxes are made square and the same size. Since this is obviously not the case, choose a consistent point to measure from (I used the back edge of each box or lid, as some were slightly wider than others).

Step 4: Assemble!

OK - if everything fits, its time to finish screwing in those metal braces. I initially planned to add cross braces to the back, but found that this construction was surprisingly sturdy - there are five points of contact for each set of boxes (two metal braces and 3 wooden dowels) so there isn't a lot of wiggle room.

I used wooden plugs to lock in the dowels. I drilled at an angle with a 1/4" drill bit, glued and hammered in a wooden plug, and sanded away the excess with the dremel. Without this step the ends of the shelves can come up, dislodging the wooden dowels.

My favorite part of this project? No sanding or finish!