Houdini made no secret of the fact that he was an expert on restraints and the skills needed to overcome them but he often concealed the exact details of his escapes to maintain an air of mystery and suspense. Although many of his escapes relied on technical skills such as lock-picking and contortion, he also performed tricks such as Metamorphosis and the Chinese Water Torture Cell, which are essentially classic stage illusions reliant on cleverly designed props. Houdini's feats helped to define the basic repertoire of escapology, including escapes from handcuffs, padlocks, straitjackets, mail bags, beer barrels, and prison cells.