Leather strap cutters are a hand-held, wooden device with a mounted leather blade that cut long leather straps from larger pieces of leather and hide. For example, if you want to make a belt from a large leather hide, a strap cutter can be used to cut off a long length of leather in a consistent thickness. It can also be used for making leather laces. Some versions are referred to as “ploughs”.
There is a means to adjust the thickness of the preferred cut, usually marked with measurements for easy reference. Blades must be kept sharp, and are replaceable if needed. Once the thickness is set, the leather is lined up and manually pulled through.
As that happens, it is cut in the thickness set, and the result is the original big piece of leather, and a strap in just the width you want it. There is a classic design of this that has been around for years that is very common and useful.