Saw Jointer with wedge

This device keeps the file at right-angles to the saw as you push down on it - and your fingers away from the teeth. It is far safer and more accurate than just freehanding a file in over big teeth. By running this file along the saw-teeth you flatten and get them in line so none are out of joint. You get more life from your file because the wide wedge can fix the file in varying positions. This exposes successive areas of the file unlike narrow metal jointers.

See it on Youtube here - https://youtu.be/FQkYzMF2HSM