If you want to cut shapes you can use the plastic under a pack of bacon or the plastic lids from butter and things like that, coffee cans. I have used the clear plastic sheets for an overhead projector. Traced with a Sharpie and cut out leaving a little of the black lines on each side where I cut out the design. I have to leave the little tabs so the stencil doesn't fall apart though. I used an Xacto knife for that. Sometimes I didn't have it wide enough for my marking pen to get inside.