Mark the Cut line
According to frame of the glass, put it on door and draw a cut line. Each frame has its two sides, outside of frame must be the one facing up and you need to mark the smaller side. In this guide we are using a fiber glass door. You can also avail other options as well. Now measure it keenly. While measuring you must keep in mind to draw a perfect square where you want to fix the glass. You have to measure it for more than once to have a perfect measurement.
Make holes by Drilling
Coming up on drilling, make holes in the corners by using drill machine. Holes must be as big as the jigsaw blade size, so that could easily fix in it. Don’t practice to drill very close to the marked line, leave some margin. For close and fine cuts you must use jig saw.
Add outer Frame
Now take out the cut. Make sure that you hold the cup until you make the final cut, for that you can use your second hand. Don’t allow it to fall out because it will tear the facing ends.
Now slowly pop in one part of frame and caulk onto the door. Make it clear that there should be sufficient caulk on all side of the frame, no worries it leak out onto the door. The imperative thing is that you don’t want any wetness/humidity between door and the frame. Now insert the exterior frame firstly, as it doesn't have any screw holes so you can guess the outside frame.