A sheet molding apparatus includes at least one molding surface having a plurality of perforations and an accompanying vacuum mechanism for controllably drawing reduced pressure through the perforations. The sheet molding apparatus includes further at least one sheet retainer with a clamping capability attached to a frame surrounding at least a portion of the perimeter edge of the molding surface. The sheet molding apparatus with the sheet retainer and its clamping capability can be used for rapidly and accurately positioning thermoformable thermoplastic sheets to match the molding surfaces in producing molded articles.