You put the mats for the cutting machines under the materials that you're going to cut. The mats have a special glue layer that keeps the material in place when you're cutting out the design. There are different sizes and the mats all have a different level of sturdiness. The sturdiness differs because different kinds of materials require a different level of sturdiness. The mats also have a protective layer on top of the glue layer. This ensures your mat is durable and that the glue layer doesn't come off.