These were used when making a jump from a bridge into a river before large crowds. The handcuffs would pass inspection, but could be opened by a tug on the wrists. Some handcuffs, called 'jumpcuffs,' could be opened by simply replacing its strong interior spring with a weak spring. He would then free himself from the difficult handcuffs, using the observer's own key. The assistant would pass the real key to Houdini, who would give the false key back to the handcuff's owner. This assistant would switch out the real key with a similar- looking key from Houdini's collection kept behind the stage. In doing so, he would allow his assistant a look at the key. To complete the act, Houdini would insist on trying the key, to make sure it worked. Houdini welcomed all 'freak' handcuffs, even if had no tool for unlocking them. With this belt, Houdini could have access to any tool he required with only slight of hand. This solved the biggest problem in handcuff work: accessibility. The inner belt ran on tiny ball bearings that could be revolved by pressure from Houdini's arm. As his skills and popularity grew, Houdini invented and used a belt made of flexible steel, containing special compartments within a double wall. At the beginning of his career, Houdini would simply conceal the keys in secret pockets or a bag strapped to his leg. It was as 'The King of Handcuffs' that Houdini first came into fame during the early years of the twentieth century. Concealing keys was simple when presenting a normal stage act as time would often not allow for an exhaustive search.

When entering a new town, the magician would research the handcuffs used by the local police as well as any 'special' handcuffs and conceal the keys somewhere on his person. Having the full set of 45 keys would allow traveling magicians the most success.

According to NEW IDEAS IN MAGIC, published in 1902, the secret to a successful handcuff act is having multiple sets of keys. Magicians began to demonstrate handcuff acts as early as the 1890s.

The handcuff king