Basically, it's double penetration via fisting, one goes in the rectum and one in the vagina, once inside, push the hands together to simulate a clap with the vaginal/rectal walls inbetween the palms.
Man1: Hey, John. Did you hear about Shelly?
Man2: Yeah, Graham did a right number on her. Sphinx clap and all!
Man1: She's destroyed.
Man2: Yeah, Graham did a right number on her. Sphinx clap and all!
Man1: She's destroyed.
by TheSecretDefiner March 7, 2011