![1girl absurdres armlet ball_and_chain barefoot black_hair braid brown_eyes crystalherb fire full_body grey_sky highres jewelry looking_at_viewer necklace original outdoors parted_lips ruins tan twin_braids walking rating:s score:27 post #2954726](/cdn_image/preview/43/1a/431a537be690382d51979cf18f9a38e4.jpg)
A heavy and dangerous to use crushing weapon that uses centripetal force for power. It uses a heavy ball-shaped weight like a flail, but the chain is longer and may not be attached to a handle.
A rule of thumb, if the weapon has a handle (especially a long handle) and the chain is under an arm's length, then the weapon is most likely a flail instead of a ball and chain.
For the restraining device, see the ball_and_chain_restraint tag.