Steel-rule die, also known as cookie cutter dies, are used for cutting sheet metal and softer webs, such as plastics, wood, cork, felt, fabrics, and paperboard. The cutting surface of the die is the edge of hardened steel strips, known as steel rule. These steel rules are usually located using saw or laser-cut grooves in plywood. In some cases, to reduce the manufacturing costs, the grooves for the steel rule are cut in a CNC router using a small diameter milling tool.
The mating die can be a flat piece of hardwood or steel, a male shape that matches the workpiece profile, or it can have a matching groove that allows the rule to nest into. See below a steel rule pressed into wooden board with grooves to create a die.