Now, place a long straight object, (e.g. a ruler or an aluminum extrusion) between the z-stepper motor and the z-profile on the heatbed (see Fig. 1).

Press the selected object against the front of the z-profile and use the lines on the heatbed to check whether it is aligned straight.

When the heatbed is aligned straight, tighten the 9x M3x12mm Countersunk Screws (silver).

If the heatbed can not be straightened even by turning it slightly, you must unscrew it again and realign the underlying y-carriage (see manuals 03.1. / 03.2.).