a method for forming sheet metal articles , such as automotive body panels , having complex curvatures . opposing , complementary , pre - form and finish - form tools are used in a single press . a sheet of hot blow - formable sheet metal alloy , heated to a forming temperature , is placed between the tools . the pre - forming tool is lowered to a first stage closed position thereby trapping edges of the sheet between binder surfaces of the tools . the sheet is first stretched against the pre - form tool using pressurized gas to form a pre - form that undergoes most of the metal stretching required for the final part shape . then the finish - form tool is pivotably advanced into a second stage closed position . the pre - form is displaced away from the pre - form tool and hot plastically formed against the opposing finish - form tool with pressurized gas to obtain the final sheet metal part shape . the finish - form tool is then pivotably retracted so as to avoid die lock or part interference conditions .