Now what is amazing for me is that someone would buy or sell this.
Years ago we used to make these out of damaged framing squares.

We just screwed a piece of wood onto the square with a couple of
sheetrock screws to bring it back into 90 degrees, just as you see in
the picture.

I remember telling the junior woodknots "go get a saw and your training
wheels so you can start doing the buildup". All 90 degree cuts, so
this was a perfect gizmo.

I always figure if I saw it out in the field everyone knew about it.

Robert