Remove the cabinet doors and set them down on a flat solid surface.
Note: It is a good idea to order extra glass in case of damage.
Slide glazing tips into place and press into the wood. Or, use a glazing gun to automatically push the tips into the wood. Put in about 12 per cabinet.
Mark your cut lines on the glass panel. Use a T-square and a glasscutter with carbide wheel (Image 1) to scribe the glass.
Run the cutter across the width of the glass. Put the tapping ball under the scribe (Image 2), apply a bit of pressure and the glass will snap off.
Do the same thing for your vertical cut. It's okay if it breaks off in several pieces. If there is a small piece left, use the teeth on the end of the cutter to break it off.
Smooth the entire length with a rubbing stone (Image 3).