Door sizes can vary particularly in the widths. When fitting a door with three hinges it is essential that the hinges do not fight each other by being different measurements. It is essential to keep the hinges straight. One way to minimise imperfections in door styles is to add hinge packers to either the centre hinge or one of both of the top and bottom hinges. This can be particularly helpful when trying to install a door to a steel or aluminium door jamb as there is not an opportunity to reassess these as would be the case with timber if that was desired. These are aluminium shims that are identical in size to a security door hinge with holes in exact required positions. They are available in the accessory section and are strongly recommended when fitting French hinged doors.