What is a an X-acto knife and mat knife?

These are both fairly common tools, found in hobby, art, and hardware stores. An X-acto knife is a small, fine blade. (Available in a variety of sizes and shapes.) It’s excellent for sculpting and slicing small parts. A mat knife, sometimes called a utility knife or box cutter, is a larger blade that can handle heavier tasks without as much risk of breaking (like slicing through thick plastic).