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How to install sliding barn doors 
Measure and cut two lengths of mounting board for each barn door. 
The boards should be as long as the doors and about 1 inch (or 4 cm) wider than the track. 
Attach the mounting boards to the top and bottom of the doorway using drywall anchors and ensure that the mounting boards run straight along the doorway.
Measure and cut two lengths of track for each barn door. Use joint brackets to attach sections of track as needed.