Designed to mount System X rails to Designer Trolley and BT8381 support columns the BT8381-JPS is a joining plate which is needed to assemble System X freestanding, mobile or bolt-down video wall solutions. The plate is fitted quickly and easily using the provided sliding nuts and countersunk screws, which allow the mounted rail to be positioned anywhere along the length of the column. A row height spacer (BT8390-SP) is also available (separately) to help position multiple rails when installing video walls, without needing to measure out the position of each BT8381-JPS.