![](https://cos-cdn.shuashuati.com/pipixue-web/2020-1231-2005-12/ti_inject-812ce.png)
The trolley slides via roller bearings on the support bar. It also transfers forces from the mechanism to the leaf and vice versa. Furthermore, it provides parallelism between the carrier and the bar. The carrier is linked to the trolley via two spherical bearings and rigidly screwed to the door leaf. It therefore transfers all weight and motion forces from the leaf to the bar.