The initial state of handcuffs and the state after handcuffs are single locks. At this time, the handcuff ring can rotate in one direction to handcuff people's wrists and handcuff people's wrists.

Plate handcuffs and chain handcuffs are two common forms of handcuffs, and the main difference lies in the connection of handcuffs. Chain handcuffs are an early design, with 2 to 3 iron rings connected in series between the handcuffs. Although this design shackles people's hands, the radius of movement formed by the length of the chain is still quite long, and the handcuffed person is still very convenient in action.