Abstract: An adjustable molding form comprises axially elongated male and female form elements made from severable plastic material. Each element has a thin-walled shell of uniform wall thickness which defines internal and external helical screw threads. The female form element has one end wall and is open at its opposite end, whereas the male form element has a pair of end walls and is threaded into the open end of the female form element. Coaxially aligned central openings in the end walls of the form elements cooperate with a rod or bolt member which extends therethrough to support the molding form at axially spaced intervals on the member.