elastic plate portion 10 b is bent at 45 u00b0 from the second elastic plate portion 10 b the extension 10 c from one end of the first elastic plate portion and the extension 10 e from one end of the second elastic plate portion are formed integrally with each other to form one l shaped flat plate and the extension 10 d from the other end of the first elastic plate portion and the extension 10 f from the other end of the second elastic plate portion are also formed integrally with each other to form one l shaped flat plate three attachment holes 10 g for attachment of a member are formed in each l shaped flat plate in the rocking fulcrum member 10 having the above described structure the l shaped flat plate portions are parallel to each other in a no load condition when a force is applied to the l shaped flat plate portions in such a direction that the l shaped flat plate portions are brought closer to each other or moved away from each other rocking on the crisscross fulcrum formed by the first elastic plate portion 10 a and the second elastic plate portion 10 b is caused the rocking fulcrum member 10 is integrally formed into a state shown in fig1 and 2 from one elastic plate member 50 shown in fig3 a large size elastic plate member is first punched with a punching press to form the elastic plate member.