The most common method for installing a wardrobe hanging rail used by the mass manufacturers is a piece of angle with triangular punched holes. This is simply screwed to the top of the wardrobe. It works OK but is an absolute beast because you have to bend down to line up the holes to insert each hanger. The method shown below was devised by multi Innovations Award winner Ray Fountain. Ray uses a piece of alluminium flat bar. He drills a series of holes and then runs an angle grinder down from the top. The huge advantage is that you can hang clothes by "feel" with no bending. Another advantage is that hangers wont jump off on bumpy roads.