This is simple and commonsensical. Great idea for making a digging fork easier to use in certain situations, like clayish or very silty soils. Offers a real foot rest (your foot can’t slip off the shoulder as easily) and by this it affords a more efficient transfer of muscular effort. For someone who can heat & bend rebar, and weld steel, it will be simple to make.
The image comes from this site: Digging Fork Mod
You’ll find a decent discussion of this little project on the page.
By the way, I’ll tell that this site itself has a lot of practical stuff on it, even though I haven’t explored it a lot as yet. Although the site is aimed at preppers (and I do not particularly identify as one), my personal feeling is that the site owner/moderator is not panic-stricken, and is open-minded and rather inclusive, non-extremist, and so on.