Watch this video from This Old House to learn how to repair sliding wood closet doors.
1 Remove the doors from the closet opening.
2 Pry tacks from groove in bottom of door.
3 Cut oak wear strips to fit into groove in door bottom.
4 Sand rail along threshold of doorway.
5 Sand top and bottom of door with 100-git sandpaper.
6 Glue oak wear strips into groove along bottom of door.
7 Lubricate all wood-to-wood sliding surfaces along top and bottom of door.
8 Replace doors and check to ensure they slide smoothly.