Planarity: Position the wheels in a horizontal position by means of a theodolite and a linear precision level with an air bubble of 0.05 mm X 1 m, check that the 4 upper generators of the wheels (detected alternately on both ends) must be contained in two horizontal planes perfectly parallel to each other, whose distance is xxxx (value shown on the drawing); in case the supports are not parallel to each other, through the lock nuts that we find under the frame we will report the minimum values (a few tenths of a millimeter) indicated on the drawings.