Picture rail. Continuing our journey up, closer to the top of the wall you'll find the picture rail. This trim piece originally served as a support to hang pictures on, as plaster walls weren't the best and could be easily damaged by all of those picture hooks nailed into the wall. Of course, with the advent of inexpensive pictures hooks that can be easily nailed into a wall to support just about any size picture, the picture rail has lost its utilitarian function. Now this piece of trim is used mostly as a decorative element to divide the wall into horizontal layers.