Rigid irons are a form of physical restraint for the limbs (and neck) wherby the restrained limbs are held at a fixed distance from each other. The restraints are typically made from steel strips bent and hinged at each end to secure the wrist or ankle, then locked together in the middle by a bolt requiring an allen key to unscrew.
Various configurations are available. Common variants are;
- Wrist to wrist.
- Ankle to ankle.
- Wrist to neck to wrist (same configuration as a pillory).
- Ankle to neck (via collar and short chain) to ankle.
- Ankle to wrist to wrist to ankle (same configuration as stocks).
- Neck to wrist to wrist (also called a Shrew's fiddle).
Because of the immovability of the restraint, rigid cuffs can be uncomfortable if worn for any length of time. This seems to be a particular problem with ankles. As a result, many manufacturers will produce designs which can be worn over boots to alleviate this probem.
Most restraints available are generally based on pre-19th century designs. However, there are a small number of manufacturers providing modern, highly engineered, versions (see Martin's Ridgid cuffs in the BDSM equipment suppliers article.