Picture rails (sometimes called picture moulding) were first used to avoid making holes in plaster or wood-panelled walls. As drywall became the wall surface of choice, their use died out, but the recent return to more traditional things, along with easier ways to attach them, has brought a rise in their popularity. Using picture rails makes sense both aesthetically and practically. Although there are no hard and fast design rules as to how to use picture rails, you will need a few materials and some creativity.
Install picture rails either at the traditional 66-inch height, or make them even with the tops of your door frames. You can also arrange them artistically around the walls at different heights. Get creative with your measuring.
Place plain or ornamental hooks securely on the tops of the picture rails, with the hook facing out and hanging down.
Attach chain, fishing line, ribbon or wire to the back of your framed picture, and loop it over the hook hanging down from the picture rail. The length is entirely up to you---you can hang one picture, hang several pictures in neat rows, or stagger them according to size, shape or even subject matter.
Stand small pictures in lighter frames on top of wider picture rails, and lean them back against the wall for a look that is more modern and less cluttered. A small ball of earthquake fixative or a padded, double-stick poster tab behind the top of the frame will help keep them from falling.
Mix and match chains, ribbon and so on for a more eclectic look.
Never set a framed picture on top of a picture rail without securing it.