Teeth 31 and 32 are formed on opposite sides of a strip portion 2 of a band 1 in the width direction. Protruding portions 51-54 are formed in a proximal portion 20 of the strip portion 2 so as to respectively engage the teeth 31 and 32 on the opposite sides of the strip portion 2 in the width direction. A release portion is provided between the protruding portions 51-54 for allowing a portion of the distal portion 22 and the intermediate portion 21 of the strip portion 2 where the teeth 31 and 32 are formed to be moved into and out of a space between the protruding portions 51-54.