Puzzle shelves

This is a half-height bookshelf made from 5 pieces of 3/4" plywood cut from a 4x4' blank according to the plan below. This prototype was made from Finnish plywood, stained with Minwax "Island Water," and treated with boiled linseed oil.

he parts have been designed to minimize wastage in the parts blank while maximizing available shelf space. The puzzle shelves unit can stand up against a wall to provide a "fourth shelf" below the other three, or it can be turned over and stand on its own.

Additionally, the prototype includes a new experimental locking halved joint which uses a foam rubber ball to keep the joined members together. The plan could easily be modified to use conventional halved joints.

Instead of flat slot-ends, the slots in the puzzle shelves unit are terminated with hole-saw cuts, giving the finished slot a kind of "keyhole" shape. When two slotted members are halved together, a spherical void is formed by the perpendicular overlap of the round cuts. A foam rubber ball, in this case a practice golf ball from the sporting goods store, is popped into this spherical recess from an oblique angle, locking the two members together and cushioning their motion against one another.