A method for locally increasing pressing pressure on a press tool having an abutment surface for being clamped onto a clamping surface in a press comprises providing a power unit smaller than the abutment surface and having an internal space, positioning the power unit between the clamping surface and the abutment surface, pressing the clamping surface against the abutment surface, connecting the internal space to a source of pressurized hydraulic fluid, and supplying the pressurized hydraulic fluid to the internal space thereby causing the power unit to expand and to exert a local pressure on the abutment surface.