Abstract: A universal digit is formed to be attachable to the residual digit of a patient, and to have a lockable joint, so as to provide considerable utility and flexibility. The structure of the joint member allows the universal digit to be easily adjusted and manipulated so that the extension portion can be locked into multiple positions by easily manipulating adjustment buttons. The extension is rotatable about a first longitudinal axis, and is further rotatable about a transverse axis which is perpendicular to the longitudinal axis. The joint structure thus has three dimensions of movement and provides a significant number of diverse options for positioning of the extension. Unique locking mechanisms within the various structures allow the universal digit to be rigidly held in the desired position, thereby increasing the utility for a patient/user.