The checkering file is just like using a triangle file, just more lines cut at a time. If a triangle file won't work, a checkering one won't either. In fact, the extra width might make it harder to use.
The technique is to use a triangular file to cut one groove at the edge of where you are going to checker. Then, use the checkering file, 2 lines only. One line in the groove you cut, and one cutting fresh. When that gets cut down a bit, then move over another groove, so one guiding, one part cut, one fresh. When you get the new one part cut, then move over two grooves. The file uses the partially filed grooves to guide on. You can't just start fresh with the whole width of the file. You add grooves until about 1/3 to 1/2 of the file is cutting fresh, and the rest is guiding and cleaning up prior cuts.
Properly used, they do a good job and speed up the production somewhat. They are better at making a uniform job than at speeding up the production, though. The smaller amount that you cut at one time with them, the faster they cut. If you try to hog the cut too much by cutting too many fresh lines, they get real slow. The only time you cut with more than half the file is when you're doing final cleanup, you can overlap about 2/3 to 3/4, and file a few strokes, then move over a random amount, do it again. Repeat until done, and do additional passes, paying attention to the final result, until you get uniformity. That last process of staggering widths helps the uniformity of the final diamonds.
dave
