Grappling Hook
A sexual maneuver wherein one is having sex with a female vaginally and doggy-style, and one inserts both thumbs (or two or more other suitable digits) into her anus and crooks them on the inside so as to create a solid lock. This creates the possibility of pulling the girl onto you more forcefully and with greater sensation. To say the least.
Grappling Hook by Der Kaiser December 19, 2004