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Use a tape measure to get the length and width of the window frame. Measuring the area will help you determine how big your new piece of glass should be. Subtract 1⁄8 inch (0.32 cm) from the measurement. The additional space will ensure that the glass will fit in the window and won't crack if the frame expands during cold weather. Go to a hardware or glass store with your measurements and buy a new piece of glass. They will cut your glass to your specifications. Let the sealer dry for one or two hours before moving onto the next step. Wood sealer will help the putty or glazing compound adhere to the wood and will help with weather-proofing your windows. This will help hold your new pane of glass in place. If you're using putty, roll it in your hands to warm it up, then apply it to the interior of the frame. If you're using a glazing compound, squeeze a tube of the compound onto the frame, around the empty hole. If your compound came in a container, use a putty knife to apply it.  Don't worry about laying too much putty or compound because you'll be scraping the excess away later. You can purchase putty or a glazing compound from the hardware store or online. Take your new piece of glass and carefully press it into the opening. The glass should press against the putty and adhere to it. Replace the clips or nails that you removed earlier by lightly tapping them back into the frame. This will help your pane of glass stay in place. Apply a layer of putty or compound around the edges of the new pane of glass. This will ensure that it's held in place with the putty on both sides of the window and will hold your new glass in place. Use a putty knife to smooth out the compound around the new window pane. Remove any excess putty or compound so that it runs flush with the frame and looks clean. Allow the putty to dry overnight so that it sets. Remember to smooth the putty on both sides of the window.
Measure the area around the broken window pane. Purchase a new pane of glass. If the frame is made out of wood, use a painter's brush to apply a layer of wood sealer around the broken window frame. Apply putty or a glazing compound around the frame. Push your new pane of glass into the empty opening. Reinsert any nails or clips that you removed earlier. Apply putty or glazing compound around the new window. Smooth the putty out and let it dry.