Abstract: An apparatus for forming a line of separation in a plastic work surface includes a tool having a tool holder of thermally conductive material, an electric heating element and a tool member having a separating point. The holder is surrounded by an insulating member and includes a sleeve portion in which the tool member is releasably secured, the tool member projecting from the body in freely exposed manner with the separating point remote from the holder whereby the work surface may be engaged solely by the separating point which comprises a tip from which a surrounding surface extends in divergent manner. The holder is arranged to conduct heat from the heating element to the tip and suitable control means are provided for regulating the heating element temperature to a desired value.