in detail in partial fig3 a and 3b has the shape of a detent slider 36 which has an activation plate 37 a guide plate 38 and two detent plate 39 and 40 are provided on the activation plate 37 each detent plate has detent elements 41 guide plate 38 and detent plates 39 and 40 are each of equal length whereby detent plates 39 and 40 as well as their detent elements 41 are identical guide plate 38 and exterior detent plate 40 lie at the side edges of activation plate 37 which is essentially rectangular whereas detent plate 39 is arranged roughly in the center guide plate 38 and detent plates 39 40 are also configured so as to be rectangular whereby the longitudinal side runs in direction a and b of the sliding motion detent elements 41 of detent plate 39 and 40 are arranged on the lateral surface that is facing guide plate 38 and central detent plate 39 detent elements 41 which are identical in detent plates 39 40 each has a detent bar 42 which runs in the longitudinal direction of detent plates 39 40 and is arranged roughly laterally in the center the length of detent bar 42 roughly corresponds to the length of.