Gim-peg

The squares are then polished in the same order, the gim peg being carefully adjusted for height between every row, in order that the stick may be inclined at exactly the same angle as that employed for cutting the squares.

Source: wiktionary

the lower end of the rod passes through a hole or mortise in the bench, and is fixed by a wing-nut beneath, in order to allow the gim-peg being twisted round to different positions, according to the distance it is required to be placed from the mill.

Source: wiktionary

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.

Source: wiktionary