How to Build a Window Seat With a Piano Hinge

Arrange two planks of 17.25 inch 2-by-2 lumber flat on the work table with 11 inches between the two planks. Sit two 11-inch planks of 2-by-2 lumber connecting the ends of the 17.25-inch planks to make a rectangular frame, 15-by-17.25 inches around the outside.

Glue the ends of the 11-inch planks to the 17.25-inch planks and let dry. Pre-drill two pilot holes, sized for the shaft of 2-1/2-inch wood screws, through the 17.25-inch planks into the 11-inch plank ends. Fasten the frame together with 2-1/2-inch screws through the pilot holes. Repeat the process so you have two frames.

Lay both frames flat on your work table and place a sheet of 1/2-inch plywood measuring 15 by 17.25 inches on top of each frame. The edges of the plywood pieces should be flush all around with the edges of the frame. Affix the plywood to the frames with 1-inch wood screws driven around the edge every 4 to 5 inches. These are the ends of your window seat.

Lay a sheet of 15-by-45 inch 3/4-inch plywood flat on your work table. This is the base of your window seat.

Stand the end panels on top of the base at each end, plywood sides out, with the 15-inch side of the end panel across the 15-inch side of the base. The plywood on the end panels will be flush with the ends of the base to form a right-angled corner. Fix the end panels to the base using four 2-1/2-inch wood screws, spaced evenly through the frame of the end panel into the base.

Position two pieces of 18-by-45 inch 3/4-inch plywood along the sides of the base. The top of these side panels should be flush with the top of the end panels, and the ends of the side panels will create corners with the sides of the end panels.

Secure the side panels to the base and end panels with 2-1/2-inch screws through the bottom of the side panel into the edge of the base, and through the frame sides of the end panels into the side panels. This completes the box of the window seat, which can serve as hidden storage space.

Paint the box of the window seat, as well as a second panel of 15-by-45 inch 3/4-inch plywood for the lid of the window seat. Let dry.

Center a 40-inch piano hinge down the length of the back edge of the window seat lid. Fasten the hinge in place using 1/2-inch screws into the pre-cut screw holes of the piano hinge.

Place the lid on top of the box, centered. Fasten the other side of the hinge to the back side of the window seat box.