You will need
1 A hot wire cutter
2 plate glass
3 a sheet of aluminum foil
4 a pan of very cold water
Start by laying a sheet of aluminum foil on an insulated surface. it should be as wide as the area you want to cut on the glass.
Lay the glass down flat against the aluminum foil
place the hot wire cutter wire on the line you wish to cut on the glass
Turn on the hot wire cutter and let it heat up and heat the glass.
After one minute of heating (time depends on glas thickness) remove the hot wire and dunk the glass quickly but uniformly into the cold water.
When the glass panel is inserted into the cold water the area thats been heated needs to enter the water all at the same time. The change in temperature causes internal forces of contraction to snap the glass instantly. Its wierd but it works.
The glass will break exactly on the line of the hot wire cutter.
Caution always be carefull of sharp edges and the proximity of water to electricity.