Hi

I am looking for advice on how to support a built in shelf above a desk area. The shelf is a custom made shelf to fit into a recessed area in the room. The sheld itslf is almost three inches thick, 8 inched wide/deep, and 72 inches long. It can be attahced to the wall on three sides, but I am worried about the middle of the shelf and that long span. Any ideas would be great!