Faux wood beams are long, hollow three-sided boxes. After installation, the U-shape faces up and the three finished sides face the room.
A hidden cleat attaches securely to the ceiling drywall. The faux beam straddles the cleat, and fasteners attach the beam to the cleat from the sides. Distressing—a way of rapidly antiquing wood—makes your faux beam look like it has been there for ages.
When two beams butt up against other, metal beam straps cover the seam. They're used for covering the ends, too, and they're easy to put on.