A typebar is an 'arm' inside a typewriter with a character on the end of it. There are generally two characters per typebar, one which will be printed if the corresponding key is struck by itself, the other of which will be printed if the corresponding key is struck while the shift key is depressed. To have letters typed in exact location, the typebar is guided all its way to the ribbon through its narrow gap in segment.
In early typewriters in the 1860s, the typebars would often jam when two or more keys were depressed simultaneously (see picture). Such jamming led to the creation of the QWERTY keyboard in 1873.[1] Mechanisms to avoid such jamming had been created by 1879, but the keyboard layout remained as the legacy of the early problem.[1]