The anal cavity of a convict, used to store valued possessions like drugs and weapons. Keistering is the fine art of stashing and withdrawing items from the prison wallet.
The anal cavity of an inmate, so named for its ability to smuggle valuables into a prision or stash them for safe keeping. Due to "recreational activity" prisoners often leave with a larger prison wallets than when they arrive.
Prison life bound to be dull, but due to years of fisting the convict managed to bring 3 kilos of smack and a boombox in his prison wallet.