Hi Judy, How long is the square end? If it is one or two inches
long, it is a "head" stake that is meant to be put into a stake
holder (called a "horse" for some reason---I have no idea why!). The
stake holder (horse) can be straight, bent, or double-ended. I put
these in the vise so that the bottom is against the lower part of the
vise, and that keeps the top from twisting out.
Another useful gizmo is the sort of thing you can find from places
like Grizzly and Harbor Freight that go over the vise jaws, and have
angles cut into them, to hold objects like stakes and pipes.
It's hard to describe these things---so much easier to show them! I
hope this helps somewhat.