A bolt-covering cap which is self-threading and gives little resistance when being threaded onto a bolt but greater resistance when being unthreaded, providing for easy installation, a tight and secure fit resistant to inadvertent loosening, and intentional removal when needed. The bolt-covering cap provides a cover shell and three angled blades which slightly deflect in one direction, requiring less turning force, and which resist deflection in the opposite direction, requiring more turning force and resisting inadvertent loosening.