A Nordfork is a device that fits behind the head of a calf to help hold it while the ground crew works (vaccinates, castrates, brands, etc.) the calf.
To use a Nordfork a mounted rider ropes a calf by the heels then drags the calf past the ground crew. As the calf goes by, one of the ground crew members slips the Nordfork behind the calf's head. As the heeler continues to drag the calf a rope and inner tube tied to the Nordfork and staked into the ground tighten. When the rope and inner tube are tight, the heeler quits dragging. The heeler continues to hold the heel rope as the calf is worked, and the Nordfork holds the front end.
When the ground crew has finished working the calf the Nordfork is easily slipped off, then the heeler releases the heels to free the calf. Using a Nordfork eliminates the need to rope the calf's head or to put a rope on its front legs.