Interlocking Burr Puzzles
Interlocking burr puzzles in Chinese are called “Lu Ban locks” (Lu Ban suo 鲁班锁). These puzzles are made of interlocking pieces that are assembled into geometrically pleasing structures that sometimes resemble burrs.
Lu Ban, together with his wife Lady Yun, is considered the patron saint of carpenters and the original master of wood joinery. Lu Ban lived in the Spring and Autumn period (770-476 BCE) and is credited with the invention of the saw, the carpenter’s plane and the ink (chalk) line. These interlocking wood puzzles were named after Lu Ban, following the tradition of many other Chinese names that pay tribute to well-known historical figures. These puzzles have also been called “six-piece interlocking cube,” “six wooden sticks,” and “Kong Ming locks” (Kong Ming suo 孔明锁, in honor of another Chinese luminary).
The interlocking burr puzzle with the simplest construction uses three rods that can be assembled into a three-way cross in which each rod is perpendicular to the other two. The most common design uses three pairs of rods, with each pair perpendicular to the other two pairs. But Chinese burr puzzles can have any number of rods, and they can be made of wood, bamboo, ivory or brass.
The rods intersect each other, but they are also interlocked so that they stay together without easily coming apart. One way to accomplish this is by cutting a notch in the center of each rod in such a way that the pieces can be assembled without leaving a void inside their intersection. When the lock structure is almost assembled, the last rod (an unnotched piece called the “key”) is slid into place. Easy to take apart, interlocking burr puzzles require much patience and an understanding of spatial relationships to put back together.
Tang Yunzhou described a six-piece burr puzzle locked together using an unnotched piece in his classic 1889 magic book Chinese and Western magic with Diagrams: Compilation of Magic:
Problem: Given six wood square rods notched in the center, put them together at the notches to make a double cross. Like the deer antler obstacles placed in front of military camps, the pieces are put together to form one structure. But once they are apart, you will have difficulty putting them together if you don’t know how. It’s an intelligence enhancing toy just like tangram and nine linked rings. It came from magicians, but now it’s being sold as a children’s toy in the market. So finding its origin is not possible.
Solution: Use six pieces of hongmu (mahogany), each about 2 cun (6.7 cm) long and with square sides of 2.5 fen (0.8 cm). Notch out each rod as shown in the diagrams. Then put the pieces together one at a time, and you’ll be able to do it. Some pieces have to be placed horizontally or vertically. Match the pieces with their character numbers in the diagram to make them fit together.
Other six-piece burr puzzles may look identical to the one shown above when assembled but have a completely different locking structure. For example, the final locking rod may have to be rotated instead of being slid into place. Other interlocking burr puzzles may have seven, nine, twelve, eighteen or more rods—or they may have different shapes. Ball-shaped burr puzzles are especially popular.
Tang Yunzhou described a ball-shaped puzzle in a sequel to his famous magic book. He called it the “osmanthus ball” because of its resemblance to the flower of that name. He wrote, “The six-stick burr consists of six square wood sticks, while the osmanthus ball consists of half-circle wood pieces that form into a ball. While one of the six-stick pieces is not notched and is the last to go into the burr to make the structure sturdy, the osmanthus ball pieces are all notched and look very similar, so it is not obvious which piece to remove first. Even if Lu Ban comes back to life, he won’t try to take it apart.”
Interlocking burr puzzles were popular in Europe as far back as the 18th century, but, as in China, there is no clear evidence as to when or how they originated.
Interlocking Burr Puzzles and Chinese Joinery
Interlocking burr puzzles have striking similarities to the construction and joinery of Chinese furniture, which itself drew on the principles of Chinese architecture. Traditional Chinese joinery never used nails, and glue was used very sparingly. As a result, furniture could expand and contract with changes in humidity and could be “knocked down” for storage or travel and then be reassembled with little more that a mallet.
It is quite possible that Lu Ban locks were used as practical objects before they became popular as puzzles. One example of this is the use of three- and six-piece Lu Ban locks as yarn winders by countryside women in Shanxi Province. While a carved piece of wood was commonly used to wind lengths of yarn, it could only accommodate one or two colors at a time. But a Lu Ban lock yarn winder with its six carved extensions allowed women to have all the basic colors at their fingertips. The joints of most Lu Ban yarn winders are very tight, so it’s unlikely that they were also used as puzzles.
Small wooden balls were also constructed using Lu Ban joinery. Some were meant to be played with as puzzles, but others were made to be worn as toggles or to be rotated in one’s hands as exercise balls.
Lu Ban joinery was also used to construct the frames of traditional bamboo chopsticks holders. People hung these utilitarian containers on their kitchen walls to hold the family’s clean chopsticks between meals. Frequently they were decorated with sayings or slogans that give clues as to their age. The frames were constructed while the bamboo was still wet and pliable, and thin bamboo and wood panels were inserted between the frame members to create open-topped compartments to hold the chopsticks. As the bamboo dried out, the Lu Ban joints became very tight and impossible to disassemble.
Jerry Slocum and Jack Botermans. The Book of Ingenious & Diabolical Puzzles. New York, 1994.
Tang Yunzhou. Zhongwai xifa tu shuo: e huan huibian (Chinese and Western Magic with Diagrams: Compilation of Magic). Shanghai,1889.
Tang Yunzhou. Zhongwai xifa tu shuo: e huan xubian (Chinese and Western Magic with Diagrams: More Compilation of Magic). [ca. 1890].