I have a 12' high wall partition that needs to be 3" inches deeper. The width of the wall partition is approximately 5". Rather than drywall the partition, I thought visually it would look much better to add a 12' piece of trim in a walnut color. Is there such an animal? The piece I would need would need to be 3" x 5" x 12'. Or is there a better way? For example, using shoe moldings or quarter-end on each side and then putting a thinner piece across the top. Or does this have to be constructed like a fake beam?