Before assembly, thin rail should be prepared by drilling. Mark the hole locations at 50 to 60 cm intervals, first drill with a 4 mm drill and then countersink with a 10 mm drill.
Then mark the walls and insert the dowels and fix the rail with the screw on the wall.
Hang the hanger to the place you see fit.
After adjusting the hook to the appropriate height, hang the hook of your picture on the hooked side of the hanger.