The RepRap Ormerod printer has 3 parts to line up on either side of the Y-Axis rods and it's possible to have an issue lining them up so that you end up with a 'twist' to the metal rods if not correctly installed. This causes the bed to appear warped.

This is a simple tool to assist with lining them up correctly.

Steps

Print 2 of these tools.
Ensure that both pieces are practically identical.
Ensure printer is on a stable flat surface.
Pieces should clip on to the rods from underneath.
Loosen the two large screws into the ally extrusion and the small screw into the T-nut on the Y210 side of the extrusion (far side).
Depending on your twist it might be necessary to do the same thing to the other side too.
Gently twist the frame until the tool feet sit exactly on the surface under the printer.
Carefully re-tighten the screws, making sure that the twist doesn't return while tightening.