Tinkertoy was developed and patented in 1914 by Charles H. Pajeau of Evanston, Illinois. Sets contained interlockable wooden spools and rods that could be combined to make a wide variety of constructions. They were marketed in different sets, according to the types and numbers of pieces included, allowing them to be both interoperable and identifiable by difficulty level (e.g. junior, big boy, grad). In addition to use as a construction toy, they have been used by scientists and students to model molecules, and even to build a primitive computer.