In the early form of linear motion bearings, a row of rods was placed under a row of skids. Modern linear motion bearings work on the same principle, but sometimes use a ball instead of a roller. The simplest rotating bearing is the bushing bearing, which is simply a bushing sandwiched between the wheel and the axle. This design was subsequently replaced by rolling bearings, which replaced the original bushing with a number of cylindrical rollers, each of which acted like a separate wheel.
This article by the east tiger chassis accessories co., LTD. Arrangement