For this purpose an auger-bit-gage, Fig.

219, p.

116, may be used, or a block of wood of the proper length thru which a hole has been bored, may be slipped over the bit, or the length of bit may be noted before boring, and then the length of the projecting portion deducted, or the number of turns needed to reach the required depth may be counted on a trial piece.

Tying a string around a bit, or making a chalk mark on it is folly.
[Illustration: Fig.137.Using a Try-Square as a Guide in Boring.] Auger-bits are sharpened with an auger-bit file, Fig.

142, p.