In the processing of flat pieces cut from sheet materials: soft metal, plastic, plexiglass — sharp edges it is desirable to remove or to blunt (to make the chamfer). The simplest tool for this is easy to do from steel strips with a thickness of 2-3 mm. in the Middle of the short sides cut with a hacksaw, and then sharpen by needle file corner; bend, as shown in the figure. Now, having a sharp groove along the edge of the plate, get two neat bevel from both sides.