How to Build a Square Wood Bed Frame

Stand up two 4-by-4-by-8-inch posts on their small ends, parallel to each other. Set a 1 1/2-by-3 1/2-by-41-inch board on top of them, and move the posts to either end of the board so their outside edges are even with the ends of the board, which is the leg support board.

Drill two holes down through the leg support board and into each post for a total of four holes. Attach the leg support board to the posts with 3-inch wood screws drilled through the holes. Repeat with another two posts and a leg support board to make a second leg unit.

Separate the leg units by about six feet and set two 1 1/2-by-3 1/2-by-77-inch boards on top of the units perpendicular to them. Spread out the two long boards so that they are at the edges of the leg units, with their outline edges even and the ends of the long boards even with the outside edge of the leg units. Drill two holes down through each long board and into each leg unit for a total of eight holes. Set 3-inch wood screws in each hole and screw them down tightly.

Position two 1 1/2-by-3 1/2-by-34-inch boards on top of the leg support boards and between the two long boards. Drill four holes through these new boards and into the leg support boards. Attach them in place with 2-inch wood screws in the holes.

Lay a 3/4-by-41-by-77-inch sheet of high-quality plywood on top of the bed frame and adjust the edges so they are even with the frame. Drill holes every 12 inches around the plywood into the frame. Set 2-inch wood screws in the holes and tighten them to attach the plywood.