A turnable wooden or metallic pin sticking in the head of an ukulele to which the end of a string is attached and wound up by turning the peg. The knob at the lower part of the peg where it is hold for turning is called wing and is commonly made of plastic, metal, or wood.

Pegs with transmission gearing are called (tuning) machines, without it friction pegs. Friction pegs are usually attached to the back of the head.

Pictures

Friction pegs of a Brueko No. 7

Rear tuning machines of a Pono MHTSH

Lateral tuning machines of a Kohala HU-212

Repairs

If a particular string does not sustain the pitch, the tuning peg is probably too loose. It can be adjusted by tightening the small screw on the back of the head knob. However, tightening the screw too tightly may damage the knob. If you loosen the screw in the middle of the knob, the peg can be completely removed and replaced with a new one.