inhook A ... releasehook A ... outhook A
The yarn inserting hook is a piece that exists on some knitting machines (including the Shima SWGN2) that helps transport the free end of a yarn to and from the knitting. This allows carriers to be brought into action anywhere on the needle bed without the long yarn tail and extra operations ("tucking in") that would otherwise be required.
inhook operation is called on a carrier, the yarn inserting hook grabs the free end of the yarn from the yarn gripper and follows the carrier onto the needle bed.
It stops a few needles away from the needle where the operation occurs.
It then waits there until
releasehook is called, which results in the yarn inserting hook releasing the free end of the yarn and returning to the edge of the bed.
outhook command is called on a carrier, the yarn inserting hook comes out, cuts the yarn, and returns it to the appropriate gripper.
Generally, the yarn inserting hook will be in while the cast-on occurs, since the structure could easily unravel. Once enough rows have been knitted to make the stitches stable, the yarn inserting hook will be brought out. Patterns will not be knit if they involve a needle that's too close to where the yarn inserting hook is parked. Note that there is only a single yarn inserting hook, so if a second carrier needs to be brought in, the yarn inserting hook must first release the yarn it is holding.