Abstract: A mould assembly for the manufacture of at least one plaster piece includes at least two parts, one being a support member (21) and the other being a mould member (22), the support member being formed of lightweight rigid material with a lower base surface (23) and at least one upwardly open cavity (24), and the mould member being formed of "rigid" film material having at least one depression (26) to depend into the cavity from at least one integral planar flange portion (27) parallel to the base surface of the support member, the inside (28) of the depression being impressed with mould detail for the plaster piece, and space (29) being afforded between the base surface (23) of the support member (21) and the flange portion (27) of the mould member (22) for accommodating at least dry plaster material for use in moulding the plaster piece.