Abstract: A unitary molding insert (24) and pin (27) of the prior art are replaced by an improved molding insert (30) which is provided with a plurality of collapsible pin assemblies (56), each including a unitary hollow, cylindrical boss (58), and a separate piston (60) having a unitary valve (62) and pin (64). Each piston (60) may be inserted in its boss (58) with its valve (62) being seated on the upper edge of the boss (58) and with its pin (64) engaging the inner surface of a mold (84) to maintain the insert (30) in a stable position during the encasing of the insert (30) with a suitable molding material. When the mold is substantially filled to capacity, the pressure created by the molding material will force the piston (60), valve (62) and pin (64) to a recessed position within the boss (58).