A turnable wooden or metallic pin sticking in the head of a 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.
Pegs for Ukuleles are attached either to the sides of the head (with the wings sticking out laterally, as is the rule with Western or electric guitars) or to the back of the head (as seen from the fretboard; corresponding to most classical guitars). Friction pegs are usually attached to the back.