Old Harland and Bluff measurement was the "peak o' your cap" if the peak of your cap fitted the gap it was close enough. Anything larger and the welder would fill it in.
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Oul scabby knuckles
If at first you don't succeed, destroy all evidence that you tried
Anything God didn't create was made by engineers.
I try so hard to make things idiot proof but they keep making better idiots