Definitions

# Disentanglement puzzle

A disentanglement puzzle is a type of mechanical puzzle that involves disentangling one piece or set of pieces from another piece or set of pieces. The reverse problem of reassembling the puzzle can be as hard as—or even harder than—disentanglement. There are several different kinds of disentanglement puzzle, though a single puzzle may incorporate several of these features.

A noteworthy puzzle, known as the Chinese rings, Cardans’ rings, the Baguenaudier or the Renaissance puzzle was Mentioned in circa 1500 as Problem 107 of the manuscript “De Viribus Quantitatis” by Luca Pacioli. The puzzle is again referred to by Girolamo Cardano in the 1550 edition of his book “De subtililate.” Although the puzzle is a disentanglement type Puzzle it also has mechanical puzzle attributes, and the solution can be derived as a binary mathematical procedure.

## Plate-and-ring puzzles

A plate-and-ring puzzle usually consists of three pieces:

• one plate or similar displaying many holes and/or indentations
• a closed or nearly closed ring or a similar item.

The plate as well as the ring are usually made from metal. The ring has to be disentangled from the plate.

Plate-and-ring puzzles have a long history and are among the first puzzles ever made.

## Rattler puzzles

Rare nowadays, the rattler puzzles were very much in fashion around 1900. These early puzzles were made from wood.

They usually consist of many smaller pieces assembled on a main piece which may have a big handle to hold the puzzle. The movable pieces have to be arranged just right to let a first piece be separated from the rest of the assembly. In this respect rattler puzzles are closely related to the lock puzzles and puzzle locks.

## Wire puzzles

Wire puzzles consist of two or more entangled pieces of more or less stiff wire. The pieces may or may not be closed loops. The closed pieces might be simple rings or have more complex shapes. Normally the puzzle must be solved by disentangling the two pieces without bending or cutting the wires.

Wire puzzles have a long history. Early examples were made from horseshoes and similar material.

More than 7000 wire puzzles are known. The mathematician Richard Hess has collected them in a book he privately publishes ('Compendium Of Over 7000 Wire Puzzles', first edition March 1991). Many of them are his own inventions.

## Wire-and-string puzzles

Wire-and-string puzzles usually consist of:

• one piece of string, ribbon or similar, which may form a closed loop or which may have other pieces like balls fixed to its end.
• one or several pieces of stiff wire
• sometimes additional pieces like wooden ball through which the string is threaded.

One can distinguish three subgroups of wire-and-string puzzles:

• Closed string subgroup: Here the pieces of string consist of one closed loop. Usually the string has to be disentangled from the wire.
• Unclosed loose string subgroup: Here the pieces of string are not closed, and are not attached to the wire. In this case the ends of the string are fitted with a ball, cube or similar which stops the string from slipping out too easily. Usually the string has to be disentangled from the wire. Sometimes other tasks have to be completed instead, such as shifting a ring or ball from one end of the string to another end.
• Unclosed fixed string subgroup: Here the pieces of string are not closed, but are somewhere on its length attached to the wire. Obviously in these puzzles the task is not to disentangle the string from the wire. One possible task may be to shift a ring or ball from one end of the string to another end.