The yellow arrow points to the U shaped metal that forms part of the mower frame.
Even with the adjusting bolt totally removed, I think there would be minimal travel in the cross member (or what I think you are referring to as the axle?). While the cross member would try to drop on one side it would be prevented by rising on the other side and hitting against the U shaped frame. There is only a few mm gap when mower is on a level surface. I might have it wrong though?
