To make a bed firmer, measure the mattress, cut plywood to match the mattress, round the corners, sand the wood smooth, and insert the board between the mattress and foundation. Use two sheets of plywood for queen-sized and larger beds.Continue Reading
Use a tape measure to determine the length and width of the mattress. For larger beds, ask a partner to help hold the end of the tape in place while you measure.
Cut a sheet of 3/8-inch plywood to the size of the bed. For queen and larger beds, divide the width in half, and cut two identical boards for the bed. If you do not want to cut the wood yourself, many home improvement stores cut plywood for a nominal charge.
Place the board under the mattress and trace the curve of the corners of the bed. Remove the board from the bed, and use a jigsaw to cut the board to fit the bed and mattress.
Use sandpaper to sand the cut edges of the plywood smooth and eliminate any splinters from the wood.
Lift the mattress off the foundation, and set the board in place. Replace the mattress on the bed.