The seperating blade opens up so that you can make an inside cut in the middle of a piece of glass up to 11" in size. Just drill a hole anywhere on the piece of glass, open up your blade while it is still in the saw, put it thru the hole, rejoin the blade and cut ! This provides you with another tool to expand your creative abilities by letting you cut intricate designs on the inside of a piece of glass just as quickly and easily as you can on the outside.