The protective caps do not only function as visually attractive completions of the locks but also close them in case they stand out too much and therefore protect them against dirt and direct access. The attached rubber ring is supposed to be put upon the thread. The rubber ring prevents the caps from getting loose. Please, screw the cap upon the rest of the outstanding thread manually until the cap is connected tightly to the security ring. The cap is made of high quality, stainless steel. You will need a protruding thread from the lock of about 3mm for the correct installation of the protective cap.