F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
F16B—DEVICES FOR FASTENING OR SECURING CONSTRUCTIONAL ELEMENTS OR MACHINE PARTS TOGETHER, e.g. NAILS, BOLTS, CIRCLIPS, CLAMPS, CLIPS OR WEDGES; JOINTS OR JOINTING
F16B23/00—Specially shaped nuts or heads of bolts or screws for rotations by a tool
F16B23/0076—Specially shaped nuts or heads of bolts or screws for rotations by a tool causing slipping of the tool in loosening rotation, i.e. disabling unscrewing unless another tool is used