I see the strait-laced OED doesn't profess to exactly understand the full 'in and out' sense of the colloquial that nuncle finds in Partridge! But it does have a description perhaps worth quoting for its sheer economical poetry:

A winding in and out, a zigzag, sinuosity.

and then there's cringle:

1. Naut. A ring or eye of rope, containing a thimble, worked into the bolt-rope of a sail, for the attachment of a rope.