Abstract: A device for unlocking a resilient prestressed catch element which is provided on a side of an insert unit. When the insert unit is inserted into an insert rack, the catch element engages in a catch opening of the insert rack with a sliding motion, as a result of the spring force of the element. A rotatably mounted unlocking lever is arranged on the side of the insert unit and the unlocking lever has a first lever section which will press the catch element out of the catch opening opposite to the spring power as a result of rotation or pivoting of the lever on its mounting. The lever has a second portion or section which will be brought into a position projecting from a front side plane of the insert unit when the unlocking lever is moved from the idle position to the position for disengaging the catch element.