The die will list what size mat to use but you don't have to cover the blades you aren't going to use. I have some dies that have several shapes on one die board. I only cover the shape I need. The blades that aren't covered will not come up and cut thus saving the cutting mat. The mat acts like the rotary cutting mat, to protect the blades when they come up. No mat, the blades do not come up. The cutting mats last a long time and they are not expensive. Buy the long die strip cutting mat, you will need that for the long die. I position my mat so it's not being cut on the same line each time.