Most handcuffs and leg irons for home use have a lever that allows them to be opened either by the user or without a key. This product features real handcuffs, similar to those used by the police, which can only be opened with a key. The double-lock function is also included. This is a locking mechanism for the engaged handcuff. When the double-lock function is activated, the handcuff cannot be closed any further. This is an important feature to prevent injuries. The locking is achieved by pressing the small pin at the top of the key into the designated opening of the handcuff.