The invention relates to a hook block base body for fastening to a pulley set of a hoisting apparatus having a plurality of deflection pulleys comprising a means for installing the hook block base body at the pulley set and a load suspension means for suspending a load, characterized by at least one projection element that is configured to cooperate with a deflection pulley on an installation of the hook block base body at the pulley set and only to permit an installation of the hook block base body at the pulley set when the deflection pulley cooperating with the projection element is rope-free.