gim-peg

noun1

1. •
   (historical) An adjustable flanged bent iron rod that rises from the workbench of a lapidary and which is used as a guide for the vertical angle when cutting facets, and also to support the arm of the lapidary.

   • A very important substitute for the gim-peg socket, already described, is the dial, by means of which facets can be cut with great precision. — 1894