A lead nipper, or cutter, is a tool used in the stained glass industry for cutting lead came.

 

Although it may look like, or be substituted for, a regular wire cutter it is not. The angle of the cutting edge is designed in a way that allows you to cut the lead and maintain a straight cut through the lead. If you were to try and cut the lead came with a regular wire cutter it will cut the lead in a v shape, which will prevent it from lining up with the adjacent piece of lead.