This is a very simple device but the manufacturer doesn't really get it. The base of the two plates holding the chisel or plane should be a flat surface. The device I received was rough, with one flat surface warped a few degrees from another flat surface. I joined two panels and milled the surfaces with a large flat file to get surfaces with some flatness tolerance. Since it's aluminum, filing was easy. Also, the jaws didn't hold the chisels very well. Rounding the sides of the cheeks with the same flat file improved grip. It is sad that the manufacturer does not have elementary quality control of the simplest devices.