Things You'll Need
Instructions
Purchase and cut wood (use a jigsaw or have the cutting done for you at the hardware store) so you have four equal lengths for the sides of the pit and a large sheet of plywood for the base. The size of the sandbox is a matter of personal choice and backyard space but 1-by-6-by-8 cedar boards cut to an equal length works well. The size of the base board will be determined by the size of the sides.
Use wood glue to attach the four cedar boards to the base board and to each other in a square. The wood glue should provide enough adhesion for reinforcement with galvanized screws. Use a wood clamp on each corner to ensure a tight, uniform fit.
Secure the wood frame in place using screws and a drill. Each side piece should be attached to its neighbor and the entire frame screwed into the baseboard, creating the tray.
Treat the wooden sand pit with polyurethane to create a waterproof seal. Use the instructions on the back of the polyurethane can to apply to wood. Allow to dry for recommended number of hours.
Calculate the volume of the finished sandbox to determine how much sand will fit inside. Sand is available at hardware stores in the concrete aisle.