The BT8390-EXT is an extension kit designed to extend rails to a desired length, perfect for creating large menu boards, video walls and other digital signage installations. The kit consists of 6 steel joining bars which fit into the channels on either side of the mounting rail. The joining bars are then held firmly together using the internal grub screws. The underside of the joining bars feature spring-loaded bearings which allows the bars to move easily into their fixed position.