Stretched galvanized clamp used as disposable formwork in work joints. Good recovery of the jets. It will be fixed to the main reinforcement using metal ties positioned at a suitable distance to contain the thrust of the concrete. It gives the artefacts further protection to the concrete and in the normal aging phase and in possible exposure to fire it prevents the sudden detachment of the iron covering. The application of plaster and external covering is considerably facilitated and guaranteed thanks to the finish that results after casting. The use allows the escape of excess water, but not the exit of the cement material, thus creating an ideal balance in the final mix.