Stained glass pliers are used to break the glass apart along the score line.  These pliers are unique in design so that you can grip the glass without chipping it. If you look at the image you will notice that one side of the plier has a flat edge for the glass to be set on and the other side has a curve on it to allow you to break the glass along the score line without chipping the glass.

 

Another type of pliers used in stained glass is the breaking plier. A greaking pliers is larger and both side have a curved edge. These are used for cutting a larger piece of glass