Hardware to suit Nu-Lock™ patio doors is narrow here: a 25kg adjustable patio door carriage and roller, which also replaces Dowell®, Lidco® and Robb & Brown™ rollers. With the range limited to a single carriage type, the part that fails on these doors is the roller under the panel — the wheel wears or seizes, the height adjustment stops taking up the slack, and the door starts grinding along the track while the frame and the catch outlast it. Because one carriage covers several brands, the check before ordering is dimensional rather than by name. Pull the old carriage out of the bottom rail, measure its body length and height, confirm it is a single wheel rather than a tandem pair, and make sure the panel sits within the 25kg rating.