Dead prisoners are kept handcuffed. The inside of your hand is made out of styrofoam. Kneecaps are ticklish. Destroying gravestones is okay if it's for Kung Fu training. People keep their fake eye in a glass of ice water.
Glass eyes are full of mints.
You can tie your tendons together. Leaves sound just like a flute if you know how to play them. You can stop someone's heart with a certain martial arts punch. Prisons have rooms boobytrapped to fill with cement. Kung Fu masters can split a bamboo pole with their tongue.