Turn off the drill's hammer action. Use a driver bit to drive 2-inch finish screws every 16 inches along the back of the shelf above the center of the top cleat. Do the same through the outer edges of the legs (not the face) into the side cleats. Set the screwheads just below the surface so they can be concealed later.
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Hammer drill with 3/16-inch masonry bit
to cut 2v4s
Comes in a kit with legs, a shelf, and interior trim.
to level the mantel.
3. 2x4 LUMBER
for cleats on which the mantel will hang. Two 8-foot pieces should do it.
4. 2 1/2-INCH-LONG 1/4-INCH CONCRETE SCREWS
for attaching the mantel to a brick chimney. If the wall isn't brick, use 3-inch decking screws to attach the cleats to the studs.
5. 2-INCH FINISH SCERWS
to fasten the mantel to the cleats. Finish screws (aka trim heads) have small heads that sink below the surface without the need to drill a countersink hole first.
6. 4d FINISH NAILS
to attach the edge molding.
7. WOOD PUTTY
to fill screw holes.
if you're painting the mantel, to fill gaps where it meets the wall.