well i have learnt something new today Thanks

I had to set up the panel saw at my Menz Shed yesterday. I could use a t-slot and DTI to adjust the fence, which was 0.2mm closer to the blade at the far end of the fence. Being a panel saw it has a travelling carriage with an adjustable fence at the back at 90° to the blade. I'd made a solid adjustable stop for this fence so it could be mitred, and return to 90°, but I couldn't think of any way to do this other than to use a big square. So I'd taken in my own framing square and a big engineer square. I didn't even think to check before adjusting, but after setting up with the framing square, I checked with the engineer square, and it was miles out. I bet there was the best part of a millimeter gap in the 500mm length of the square! The Shed had three framing squares, which turned out to be worse than mine - and one of them was steel. Anyway, I heard of the trick you used, but not tried it, so I'll let you know if I can fix my squares. BTW I bought a so called precision square from Bangood a while back, and the legs were not even parallel, so that's the first thing I'll be checking.

The tool he was using is called a nail set. You’re welcome.