Further, with the metallic parts 11 and 21 in the coupled state, the longitudinal dimension L is greater than the transverse dimension S and the assembly of {TAIL ~ the metallic parts} 11 and 21 is roundish as a whole, so that when the coupled metallic parts come into {HEAD ~ contact} with the users body, they will automatically roll thereon until they assume a transverse position, i.e., a position in which the coupled direction of the metallic parts extends along the users body 
Further , with the metallic parts 11 and 21 in the coupled state , the longitudinal dimension L is greater than the transverse dimension S and the assembly of { TAIL ~ the metallic parts } 11 and 21 is roundish as a whole , so that when the coupled metallic parts come into { HEAD ~ contact } with the users body , they will automatically roll thereon until they assume a transverse position , i.e. , a position in which the coupled direction of the metallic parts extends along the users body
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