There are two styles of folding doors: bifold and accordion. To work correctly, each must be plumb and hung from level track. The track, pivots, pivot brackets, slide guides, rollers, and other hardware are supplied with them.
To hang a pair of bifold doors, first install the track, complete with two top pivot brackets and a plastic or rubber snubber to cushion the impact where the doors meet. Push one pivot bracket to the wall and drop a plumb line from its center to the floor. Install a bottom pivot bracket at that point. Put the door’s bottom pivot into its bracket and slide the top pivot bracket toward the center until you can slip the top pivot into it. Then slide the bracket back, inserting the spring-mounted slide guide into the track, and tighten the setscrew. Make any fine adjustments with the horizontal and vertical adjusting bolts. Hang the second door in the same way. Then close the doors and mount a pair of aligners near the bottom on the back.
To hang an accordion door, first position the track and mark the screw holes. With the doors tied or taped shut, slide the rollers onto the track. Then screw the track in place. Drop a plumb from both ends of the track; use one as a guide for attaching the door’s hinged wall panel and the other for placing the strike plate into which the latch fits.