The method includes providing a mold apparatus (1) that includes, a first mold portion (11) having an interior mold surface (14) having a plurality of perforations (26) and a perimeter edge (17). The mold apparatus (11) further includes at least one tubular sheet retainer (35) having an exterior surface (38) having a plurality of perforations (41) and a longitudinal axis (44) that is oriented along at least a portion of the perimeter edge (17) of the first mold portion (11). Each tubular sheet retainer (35) is reversibly and controllably: (i) positionable along an x-, y- and/or z-axis relative to the perimeter edge (17); and (ii) rotatable around its longitudinal axis (44), toward and/or away from the perimeter edge (17). A heated thermoplastic sheet (95) is formed and contacted (while at a thermoformable temperature) with the interior surface (14) of the first mold portion (11) and the exterior surfaces (38) of the tubular sheet retainers (35). Reduced pressure is drawn through the perforations (41) of the tubular sheet retainers (35) thereby retaining a portion of the heated thermoplastic sheet (95) thereon. The tubular sheet retainers (35) are rotated and/or moved along the x-, y- and/or z-axes with the sheet retained thereon, relative to the perimeter edge (17). Reduced pressure is drawn through the perforations (26) of the interior mold surface (14), thereby drawing the heated thermoplastic sheet (95) into intimate contour matching contact there-with.