The invention relates to a back gauge (15) for a back gauge positioning system of a bending machine. The back gauge (15) comprises a stop finger (18) on which at least one stop surface (17) is configured, a base unit (21) that is configured for coupling with the back gauge positioning system (14), wherein the stop finger (18) is coupled with the base unit (21) by means of a linear guide (29), and the stop finger (18) can be displaced relative to the base unit (21) between a pushed-forward working position (28) and a retracted position (30), characterized in that the stop finger (18) and the base unit (21) are coupled with a first spring element (34), by means of which the stop finger (18) is pre-loaded into its working position (28), and that a locking device (41) is configured, by means of which the stop finger (18) can optionally be locked in the working position (28) or is released into its retracted position (30) for displacement counter to the spring force of the first spring element (34).