Abstract: A generally cylindrical body is molded from a soft plastic such as polyethylene. A reduced diameter coupling boss is formed at one end of the body, projecting from an alignment shoulder. An exterior alignment flange is formed at the other end; and a coupling recess is also formed in that other end having a diameter for a friction fit with the coupling boss of a mating natch body. The body includes means defining a relatively large retainer flange intermediate its ends, having opposed recesses so that its periphery is noncylindrical. Natches of this configuration are used as mating natches for both parts of a two part mold, with the alignment shoulder and alignment flange coinciding with the parting lines of the respective mold parts.