If you have a sliding window, one of the panels will be stationary, and the other will slide back and forth. If the slider is the one broken, you simply lift up and swing the bottom out. If the bottom won't come out, check for rollers on top. Sometimes the top rollers are adjusted up so the slider can't be removed. Just loosen the screw holding the roller in place and lift up with some force. That should push the rollers down, allowing you to remove the panel. Lay the panel on a table and measure the width and height of the glass only. Take this measurement and add 1/2" to both the width and height. This is the size of the new glass that you need to order. Measure the thickness of the old glass. It will either be 1/8" or a little less than that. The thin glass is called single strength and is actually about 3/32". The 1/8" glass is called double strength glass. Be sure to order the right one. If you order double strength glass because you figure it's stronger than the old single strength piece, you are going to have a devil of a time putting the frame back together. That tiny 1/32" difference can be a real pain in the neck. Trust me, you want to replace single strength with single strength.
Now, it's time to take the frame apart and remove all of the old glass. Make sure to put on a heavy pair of gloves to avoid getting cut. You will find a screw in each corner of your frame. You want to remove two of these screws in opposite corners. So, if you remove the bottom left screw, you need to also remove the top right one. Now, take a rubber mallet, slide one of the corners off the table that has the screw removed, and tap the frame to separate it from the glass. Set that half of the frame aside, then do the same thing to the other half. Now you should have two halves of the frame, a piece of rubber, and lots of glass. Throw away all the glass, then clean out the rubber, making certain to get every piece of glass out of there.
When You get the replacement glass home, lay it on the table with one long and one short side hanging over the edge. Put the rubber on those two overhanging edges. Put one half of the frame (it doesn't matter which half) against the glass and tap the corner on first. Then tap the long edge onto the rubber until it seats. Then do the short edge. Now, put the other two edges over the table and do the same procedure. Finally, install the screws in the corners. Put the panel back in and you're done.
If the broken pane is the stationary portion, there is a little extra work to get the panel out. You need to take out the slider first, then remove the two screws holding the center bar in place. Tap the center bar away from the panel until it is off the side of the panel. Set it aside. Then tap the frame edge to pull it out of the channel attached to the wall. Once it's away from the side channel, you can lift it up and out like you did with the slider. You remove and install the glass in the frame just like you did with the slider, put the frame back in the opening, tap it into the side channel, install the center bar and screws, and install the sliding panel. That's it! You're done.
