How to Make Your Own Cement Benches

Set the larger plywood sheet on your work surface. Stand one 48-inch board upright on a long edge. Butt the side of the board against a long edge of the plywood, forming the shape of an L. Insert wood screws, evenly spaced, through the side of the board and into the plywood along the lower edge using a power drill with a Phillips attachment. Attach the other 48-inch board to the opposite long side of the plywood in the same manner.

Butt one 22-inch board upright and on a long edge against a shorter end of the plywood and board assembly. Insert screws, evenly-spaced, through the side of the board, into the plywood and both vertical boards. Attach the remaining 22-inch board to the opposite open end in the same manner, completing an open box.

Set one smaller plywood piece on your work surface. Butt one 16-inch board upright and on a long edge against the side of the plywood. Insert screws through the board and into the plywood. Attach another 16-inch board to the opposite side of the plywood in the same manner.

Stand one 17-inch board upright and on a long edge. Butt it against one shorter end of the assembly. Insert wood screws through the board and into the plywood and both vertical boards. Attach another 17-inch board to the opposite end in the same manner, completing one smaller, open box. Repeat with the remaining plywood and boards to fashion a matching, smaller box.

Mix the concrete with water in a wheelbarrow according to the manufacturer's directions. Stir it with a shovel. Pour wet concrete from the wheelbarrow into the bucket.

Pour 1 1/2 inches of concrete into each of the box molds. Set the longer rebar rods side-by-side, equally spaced, on top of the wet concrete in the larger mold. Set three shorter rebar on top of the wet concrete in each of the smaller molds. Rebar rods support the concrete and help make it stronger. Pour another 1 1/2 inches of concrete into the molds, covering the rebar.

Tap the sides of the molds gently with a rubber mallet to help air bubbles escape. Allow the concrete to set and cure according to the manufacturer's instructions, at least 48 hours.

Remove all screws from the molds and disassemble the boxes. Stand both smaller concrete sections upright with a 3-inch-wide and 16-inch-long edge vertical and facing you. Space them 40 inches apart.

Apply a generous bead, or stripe of masonry adhesive across the tops of the upright sections. Center the large concrete section flat and horizontally over the upright sections and set it on top. Press down to help it bond with the masonry adhesive.