AbstractMolds used for low pressure forming of rubbery polymeric sheet have certain design constraints. The choice of mold material depends upon the severity of service and the number of parts required. Specifications for wood, plaster, aluminum, thermosetting resins, sprayed metal, and steel are discussed. Design criteria for vent hole diameter and number of vent holes are presented. Frictional aspects of mold surfaces and ancillary aspects of mold design, such as clamping mechanisms and sheet supports, are discussed.