It is a piece of plexiglas that has laser etched lines to guide you in mitering the corners of your mini albums, books, journals or other projects. It is a quality made product, made in the United States. It is designed to be used with a rotary cutter, knife, or pencil and scissors as desired. You can use it for spacing your covers, or cutting a 45 degree "hinge" for box construction. Some clever artists even use it for a cutting edge for their tape.