Knuckle

hinge Knuckle

The Knuckle of a hinge is the part of the leaf that wraps around the pin.

Most hinges have simple knuckles as shown here, but there are two interesting exceptions: Extruded hinges and double wrap hinges.

Knuckles come in inch-relative sizes, like half inch, three quarter inch, full inch, etc. Custom knuckle sizes are extremely rare and expensive.