That is what your sight pins are for aren't they?

Anyhow, I would be leary of relying on something like this. It isn't that hard to judge out to 35 yards is it?

With that said, I walk around everywhere now guessing and checking myself since I got my Nikon. It is always in my pocket, even when I go to work. I am within 2-3 yards every time at 40 and closer.