Fisting
Fisting is inserting an entire hand — and sometimes part of the forearm — into a partner's vagina or anus. Despite the name, it's not a punch: the hand goes in slowly as a narrow cone, then curls into a fist once inside. It's an advanced act demanding patience, huge amounts of lube, and gradual warm-up, usually building up with fingers or toys first. The draw is extreme fullness and the profound trust it requires. It's very much a 'work up to it over time' practice, not a first-date move.
For the receiver, the sensation of complete fullness is uniquely intense, and reaching it takes such trust and surrender that it can feel deeply bonding. For the giver, being allowed inside so completely — literally holding a partner from within — is an intimate, powerful act of care and control.
After lots of warm-up and lube, the giver draws their fingers and thumb together into a tapered cone and eases in gradually, letting the receiver control every inch, then curls into a loose fist once past the widest point. Movement is slow and minimal; the receiver stays in charge throughout.
Go slower than you think, use enormous amounts of thick fisting-specific lube, keep nails trimmed and wear a glove, and never push past pain or resistance — the receiver is fully in control. Build up over many sessions rather than forcing a goal; anal fisting is higher-risk than vaginal. Stop for any pain or bleeding, and seek medical help for sharp pain, heavy bleeding, or lasting discomfort.