Although intended for round bar I guess one of these would work on
square also if it was level.

http://www.jlindustrial.com/catalog/...&id=PEC-42100J

a6016 wrote:

A friend, who died of cancer about a year ago, was working in his shop
one day while I looked on. He was drilling a hole in a piece of 2"
square tube to make into a trailer hitch. He had a little tool or
device that he used to find the center, side to side, to drill the hole
into which the retaining pin would be inserted and secure the hitch.
Does this "thing" sound familiar to anyone? I'd like to find it for my
own use.