Double wishbone suspension 

When doing a vertical 69, with your feet on the ground and her legs straight up in the air. Put both elbows straight out with your hands at your chest/her crotch. Split each hand into two sets of two fingers (pointer & index fingers, ring & pinkie fingers), like Spock. Insert both sets of ring & pinkie fingers in her anus, insert both sets of pointer & index fingers in her vagina. Then proceed to curl all fingers and move your forearms/her body up and down vigorously, holding on inside of her.

Double wishbone suspension by Roostafy April 21, 2003