witness marks

A witness mark is a mark made by the builder of a machine- or a firearm- that indicates the place where two parts line up- or where they should.
It’s also used to refer to the spot on a machine where two items have made repeated enough contact. The spot where a bumper hits the frame on an offroad vehicle, the place where a cam follower rubs agains the cam, the spot where your keys rub the dash smooth hanging from the ignition.
On my tractor, there’s a spot where if you stick your fingers through the spokes you touch the steering column. I never noticed I do this, I just do. Now that I have noticed it, I remember dad doing it too.
And today, I noticed, that the years and years and years of sticking my fingers through the spokes as I steer and dad doing the same, the paint has worn completely through. We’ve left the same witness mark on the tractor, father and son, thirty years of doing the same thing.
I think about the other things Dad did that left their mark, and I realize that some of those witness marks were left on me. And I’m trying to leave them on my child. What witness marks do you bear? Where will you leave your witness mark?

-->