Measure your window’s width and height with a measuring tape.
Add 7 inches to both measurements. For example, if your window measures 30 inches wide by 64 inches tall, then your total measurement would be 37 inches wide by 71 inches tall.
Purchase a 5/8-inch-thick plywood board to match the measurements of your window, plus 7 inches. Plywood boards usually come in 4-foot by 8-foot sections and can be cut to size for you on-site by the hardware store's employees.
Place the plywood board over the window so that the board sticks out 3.5 inches around the entire perimeter of the window.
Drill 2-5/8-inch screws into each corner of the board, directly onto the studs around the window. If the walls of your house are made of concrete, then you can drill the screws directly onto the wall, but you’ll have to use a hammer drill to predrill the holes for the screws and then drill in the screws.
Drill an additional 2-5/8-inch screw every other 6 inches around the entire perimeter of the plywood board to secure the shutter in place. Drill these screws either into the studs or the concrete wall, depending on how you drilled the screws on the corners.