Abstract: A rubber thimble has a novel structure and prevents a user from feeling pressure from a reinforced ring formed on the upper peripheral part. The rubber thimble has a reinforced ring on the upper part of a thimble body to enable easy retrieval of the rubber thimble from a mold during the manufacture of the rubber thimble, as well as prevent the upper end of the thimble body, which is very thinly manufactured, from tearing easily, and enable the user to accomplish a basic function of wearing the rubber thimble on a finger or taking the rubber thimble off the finger by holding the reinforced ring. A plurality of weak parts formed on the reinforced ring reduces the elasticity and strength of the reinforced ring, thereby preventing the reinforced ring from applying a strong pressure to the user's finger and causing numbness or pain to the user's finger.

Abstract: After a bolt (3) and a double-structured nut (6) are fastened to each other, it is not possible to unfasten the bolt (3) and nut (6), because a predetermined part of the nut (6) is designed to break when subjected to a predetermined torque necessary for fastening the nut (6), and thereby permitting the remaining part of the nut (6) to remain fastened securely to the bolt (3) after the fastening operation of the bolt (3) and nut (6) is performed. The nut (6) double-structure including a cylindrical cover member (7) may alternatively be utilized for a similar double-structured bolt head (42) having a protective cover (43).