They are often equipped with D-ring attachments or buckles to fit nylon webbing restraints.
They are typically used as a set of four to attach each wrist cuff (directly or indirectly) to the corresponding ankle cuff, thus putting the wearer in a sexually vulnerable position. Alternatively, a pair of ankle cuffs can be used together with thigh-width straps to create a frogtie.
They can also be used in conjunction with leg spreaders.
Note: as with all bondage activities, care must be taken. All the dangers associated with physical restraint apply to the use of bondage cuffs. No-one should ever be left alone when restrained. Bondage cuffs are not suitable for suspension bondage. You are responsible for your own and your partner's health. See also safe, sane, and consensual.
See also: Testicle cuffs, handcuffs