Bob Paddock writes in mailing list item 4747: I can shed a bit of historical light here. [...] It was a different era ~20+ years ago when this was done to solve a specific problem of the day. I was the one that came up with the vendor mapping concept and Dan implemented. I think I was the one that added the RegEx code to solve a multiple vendor problem. At that time, ~20 years ago, APCircits was the primary provider of low cost boards. To use the service they had a very small drill rack that could be used and a small set of allowable clearances. Also the libraries of the day had nothing in common as far as drill/whole sizes. [...]