" Older homes often have single-pane glass windows. While not as energy efficient as modern multi-pane glass, they can easily be repaired at home if they are damaged. In this case, the cracked pane of glass to be replaced is in the second floor window. So, it'll be safer and easier if we take the window sash out of the window and repair it where we can work in a safe place. Window sashes are held in place by pieces of wood called stops. If the stop is nailed in place, carefully pry it away from the window casement. In this case, the stops are held in place by large screws for easy access. Using a utility knife, cut the paint along the edge of the stop. By scoring the paint, when the stop is pulled away from the sill, the paint is less likely to crack and peel. We'll only need to remove one stop to remove the sash. With the stop removed, slide the sash up and out of the window frame. If there are counter weights attached, you'll need to detach them from the sash. Lay the sash outside up on a solid level surface. Using a sharp chisel, chip away the hardened putty that seals the glass in place. Every few inches, you'll run into a metal glazier's point, which are small bits of metal that hold the glass in the frame. Pry the glacier's point loose with a screwdriver and remove the stubborn ones with a long nose plier. Once the putty in the glacier's points have been removed, removed the glass wearing safety glasses and heavy work clothes. If the glass will shatter, it's easier to remove the shards of glass first and then remove the putty. When the glass and putty are removed, check first to make sure that the window is square, and then proceed to measure the width and eventually the height of the opening. When ordering the glass, subtract an eighth of an inch from the height and the width of the actual opening in order to make sure the glass fits. Before you insert the new glass, coat the inside of the frame with boiled linseed oil. This will keep the dry window frame from prematurely drying and cracking the new glazing compound. Next take a ball of glazing compound and knead it in your hands to soften it. Make a thread of the glazing compound about an eight of an inch in diameter and press the glazing compound along the edge of the window frame. This becomes the bed that the new glass will rest on. Gently press the new glass into the bed of putty, sealing it in place. Secure the glass in place by pressing glazier's points every four to six inches around the glass. Press the glacier's points into the window frame with a stiff putty knife or chisel. Soften another batch of putty by kneading it well and roll it into a strand about three eight's of an inch thick. Starting in one corner press the putty along the edge of the window frame shaping it into place as you work your way around the frame. Use a clean putty knife dipped in turpentine to smooth the putty. Hold the putty knife at an angle. Using the edge of the putty knife as a guide and make a neat beveled edge. Remove any extra putty as you go. Checking to make sure that the putty isn't visible from inside the window when you look out. Allow the putty to dry for day before painting it to match the rest of the window. The windows sash goes in the same way it came out. Slide the sash behind the stop and lower it into place. Replace the stop against the window casing and replace the screws or other fasteners to secure the stop in place."