The X bar is the cross member that the foot rest system mounts to on a Multi Frame:x. It carries the foot plates and holds them square, which is what stops the supports drifting out of position under a child who pushes hard through their feet.
Because the foot supports hang off it, the bar is also what allows the whole foot rest assembly to be angled and set as one unit. It is a structural part of the frame, so it is normally ordered with the foot rests it carries.






