side-bearing

from The Century Dictionary.

• noun In car-building, a supporting plate on a car-truck. Such plates are arranged in pairs on each side of the center-bearing (which see), the body-bolster side-bearing and the truck-bolster side-bearing forming an opposing pair. Normally, the weight of the car rests upon the center-bearing, the side-bearings being designed to prevent excessive rocking of the car when it is in motion.
• noun A bearing so constructed as to limit side motion.