with the roller 50 by way of example the same explanations are also valid for devices comprising only the connection pin 52 or a connection pin 164 that runs within the elongated opening 48 and that will be described in more detail later on fig4 a shows an arrangement wherein the jaw parts 22 and 24 are closed comparable to the representation of fig2 in this state the force transmission element 30 as well as the connection element 36 and consequently the latching element 38 are in their furthermost proximal position in this position the roller 50 is arranged within the elongated opening 48 between the distal end of this elongated opening 48 and the first projection 64 u2033 of the longer wall 60 in order to get to the first opening step as it is shown in fig4 b the latching element 38 has to be moved distally this is done by a distal movement of the connection element 36 via the force transmission element 30 this movement is implied by arrow 68 of fig4 a and can be done by an operator by pushing the operating element 20 for example by the force applied on the latching element 38 the roller 50 is able to overcome the barrier given by the projection 64 u2033 accordingly the roller 50 reaches a position as shown in fig4 b in this position the roller 50 is arranged between the projections 64 u2033 and 64 u2032 the roller 50 now lies in a well 70 this well 70 is formed by the projections 64 u2032 and 64 u2033 in order to avoid a loose arrangement in this well 70 the roller 50 is held in this well additionally by the.