Sex involving insertion of the hand into the anus. Though possible, rarely is the hand initially inserted while balled in a fist. The hand enters the anus slowly while the fingers are straight and together, then balled into a fist once fully inserted. "Punching" is the term used when the hand is forcefully inserted while initially in a fist. Done properly, anal fisting stimulates the prostate.
Do all gay men anal fist?
The number of gay men that enjoy gay fisting is small compared to those that enjoy other sexual activity.
Are gay men the only ones that fist?
No, heterosexual women, lesbians and a fraction of straight men also engage in fisting.
Where can I learn more about fisting?
A Guide to the Sensual and Spiritual Art of Handballing is an informative guide on the mental, physical and spiritual aspects of fisting.