System which comes with the mantel to hang it is too lightweight, I do not recommend using if you plan to put anything remotely heavy on the mantel.  If you do use the 45 degree wedge to mount the mantel pre-drill so the wood doesn't split.  *Best is to use a 2" x 4" cut to fit inside mantel box - mount the 2x4 to wall, center and level over fireplace.  Slip mantel over 2x4 and counter sink/pre-drilling ~ I used 2 1/4" 8-gauge cabinet screws (every 10 inches on top and two on sides).