A connecting piece couplable to a rail of a weapon is described. An example connecting pieces includes a first retaining element including a first receiving region configured to engage a corresponding first counterface of the rail. The example connecting piece also includes a second retaining element including a second receiving region configured to engage a corresponding second counterface of the rail. In addition, the example connecting piece includes a guide slot running diagonally to a longitudinal direction of the rail via which the first retaining element and the second retaining elements are coupled. When one of the two retaining elements is displaced in the longitudinal direction of the rail, at least one of the first retaining element or the second retaining element moves obliquely relative to the other of the first retaining element or the second retaining element following the orientation of the guide slot to move the connecting piece between a working position in which the first receiving region is engaged with the corresponding first counterface and the second receiving region is engaged with the second counterface to a release position in which both the first receiving region and the second receiving region are no engaged with the corresponding first counterface and the second counterface, respectively.