That telescopic arm was probably designed to decrease static room which strongly matters in my shop but I met recurrent troubles with the rollers and made the decision of fixing the issue. Weak roller thurst bearing was not able to withstand the numerous back and forth of the wagon carriage I sometimes need to cut small stocks. As workaround, I built a crosscut fence waiting for an aftermarket mitre gauge that did not require for the setting of the side support table and the scaled fence. Be that as it may, the roller demanded help to properly work.

So I unscrewed the extension bar stop then removed the housing and the tube. Four rollers with their two roller thurst bearings held and guided that bar and the top sweeper cleaned the tube from dust as you may see in the below picture.

The front below roller and top rear one only supported the bar whereas the two others purposed guidance. The four roller kept their guidance abilities and I added ball bearings in order to replace the held capacity of the front below and top rear rollers. But the below picture is worth a thousand of words. Although not mechanically inclined and the lack in accuracy resulting, it has well worked since the end of the previous century.