I've never really liked the adjustable depth stop on my DeWalt 621. There are only three steps and the screw lengths are so different that I never seem to be able to arrange them to 1/8" apart. I've always thought a much better guide would be a simple set of steps, 1/8" apart. After procrastinating on this for well over a year, I finally took up an offer from a friend who has a 3D printer. I measured the guide, made a simple drawing, and three days later I got the part back in the mail. For those not familiar with the DW621, here's the stock model:
Here it is with the new guide. A bit hard to see, because it's black ABS, but the new guide has four steps, exactly 1/8" apart. No muss, no fuss, no wondering it's gotten out of adjustment.