The instrument (1) has two clamping jaws (5, 6) at an end of a shaft or a gripping part. A separator (10) is movable parallel to the longitudinal axis of the instrument in an intermediate space provided between the clamping jaws. A bearing pin has an opening extending along a moving direction of the separator, where the separator is inserted through the opening such that the largest extension of the opening transverse to the moving direction of the separator corresponds to the dimension of the separator in the moving direction.
