How to Board Up a Window
To board up a window, try using plywood. First, measure the height and width of the window so you know how much wood you'll need. Then, cut a piece of plywood so it's 8 inches higher and wider than the window. If your window is larger than the piece of plywood, attach 2 pieces together by screwing a 2 by 4 along the seam between the 2 pieces of wood. Next, drill holes about 2 inches from the corner of the plywood, which should line up with the studs in the wall when you screw it in place. Drill additional holes at 12 inch intervals around the board. Finish by placing the board over the window and screwing it into place.
Record the vertical and horizontal measurements for the window. Use a tape measure to determine the height and width of the window you plan to board up and write these measurements down. If the window has an extended sill, measure vertically from the top of the sill to the top of the window. When measuring horizontally, measure inside the window's exterior trim. Cut a piece of plywood that is 8 inches (20 cm) higher and wider than the window. Add 8 inches (20 cm) to the height and width measurements you took of the window, then use these new measurements to measure and cut your plywood. Use a circular saw to cut the plywood. For example, if your window measures 48 inches (120 cm) tall and 24 inches (61 cm) wide, then your piece of plywood should be 56 inches (140 cm) tall and 32 inches (81 cm) wide. If the window has an extended sill, you only need to add 4 inches (10 cm) to the height before cutting the plywood. If you don't have a circular saw, you can take your plywood to a home improvement store to have it cut for you. Attach 2 pieces of plywood together if you need a bigger piece. Most pieces of plywood are 4 by 8 feet (1.2 by 2.4 m), so if your window's dimensions are larger than this, you'll need to use 2 pieces of plywood attached to each other. Place 2 plywood pieces next to each other, then lay a 2 by 4 in (5.1 by 10.2 cm) bracing along the seam. Finally, drill 2.25 in (5.7 cm) screws through the bracing and into the plywood to attach them all. Drill at least 6 screws (2 at the top of the bracing, 2 in the middle, and 2 at the bottom) through the bracing and into the 2 pieces of plywood to make sure they're securely attached. Use a stud finder to find the studs in the wall around the window frame. You'll want to make sure you're not attaching the plywood merely to trim around the wall, since this won't be secure. Look for the studs 4 inches (10 cm) out from each side of the window frame. If you don't have a stud finder, you may be able to determine where the stud is by looking for nailheads in the siding, since these nails have probably been nailed into the stud. Drill holes in the corners of the plywood that align with the studs. Drill 4 holes that are each around 2 inches (5.1 cm) in from the edges of the plywood at each corner. You may need to adjust this measurement to ensure that the holes you drill will line up with the studs in the wall when you go to screw in the plywood. Make sure the holes you drill are equal in diameter to the screws you will use to attach the plywood to the wall. Use ⁄ 4 in (0.64 cm) pan-head or lag screws for the best results. These holes in the plywood are called “pilot holes.” They should be drilled all the way through the plywood. Make additional holes at 12 in (30 cm) intervals around the plywood. These holes are where you will screw the plywood into the wall. Align these holes with the corner holes you already drilled to ensure that these new holes will also line up with the studs in the wall. If the window has a sill that extends out at the bottom, you only need to drill these holes on the top and sides of the plywood. These holes should also be around 2 inches (5.1 cm) from the edge of the plywood. Note that the holes in the top and bottom of the plywood will not be screwed into the studs in the wall. Place the plywood over the window frame and use a drill to screw it in. Have someone hold the board while you drill screws through each of the pilot holes, or vice versa. Use pan-head or lag screws that will penetrate at least 2 inches (5.1 cm) into the framing. These types of screws are best since their flat-bottomed heads won't sink into the plywood and weaken it. Use corrosion-resistant screws if you're boarding up your window in advance of a hurricane or other major storm. Measure the height and width of the window you’re boarding up. Determine the height and width of the window with a tape measure, making sure to write your measurements down. Measure from the top of the window frame interior to the bottom, as well as from side to side. Don't measure beyond the frame itself. Your plywood piece will be cut to fit inside the window frame, so there's no need to measure beyond it. Cut a piece of plywood to match the window’s dimensions. Use a circular saw to cut the plywood to match the height and width of the window frame. You'll be placing the piece of plywood snugly within the frame, so the measurements of the plywood should be as close as possible to the dimensions of the window. For example, if your window frame measures 48 inches (120 cm) tall and 24 inches (61 cm) wide, then your piece of plywood should be 48 inches (120 cm) tall and 24 inches (61 cm) wide as well. Take your plywood to a home improvement store to have it cut for you if you don't have a circular saw. Use 2 pieces of plywood attached to each other if the frame is too big. #*You'll need to use 2 pieces of plywood attached to each other with a 2 by 4 in (5.1 by 10.2 cm) bracing along the seam if your window frame is bigger than 4 by 8 feet (1.2 by 2.4 m). Place 2 plywood pieces next to each other with a 2 by 4 in (5.1 by 10.2 cm) bracing placed along the seam. Then, drill 2.25 in (5.7 cm) screws through the bracing and into the plywood to attach them all. Drill at least 6 screws (2 at the top of the bracing, 2 in the middle, and 2 at the bottom) through the bracing and into the 2 pieces of plywood to make sure they're securely attached to each other. Use a hammer to attach 4 window clips to the sides of the plywood. Place 2 clips on each side of the plywood, positioned so that the tension legs are facing towards you. Then, gently tap the clips with the hammer to attach them to the plywood. Be sure to place each pair of clips no more than 2 feet (0.61 m) apart from each other. Position the clips so that they're evenly spaced from each other for best results. You may be able to simply push the clips into place. However, using a hammer will ensure that they are as securely attached to the plywood as possible. Place the plywood over the window frame and push it in to secure it. When you do this, make sure the clips are securely gripping the sides of the frame and aren't being pushed out of it. Push the plywood as far into the frame as it can go. Strong winds generate lift on the plywood that can cause it to be pulled out of the window frame. If the window clips are securely gripping the sides of the frame, they will keep the plywood in place. When you're ready to remove the plywood, simply push down on the board and pull up on the window clips on 1 side to remove it. 
Record the vertical and horizontal measurements for the window. Cut a piece of plywood that is 8 inches (20 cm) higher and wider than the window. Attach 2 pieces of plywood together if you need a bigger piece. Use a stud finder to find the studs in the wall around the window frame. Drill holes in the corners of the plywood that align with the studs. Make additional holes at 12 in (30 cm) intervals around the plywood. Place the plywood over the window frame and use a drill to screw it in. Measure the height and width of the window you’re boarding up. Cut a piece of plywood to match the window’s dimensions. Use 2 pieces of plywood attached to each other if the frame is too big. Use a hammer to attach 4 window clips to the sides of the plywood. Place the plywood over the window frame and push it in to secure it. 