Beam Bracket, 4" X 4" X 3.5” Heavy Duty Corner Bracket. Fireplace Mantel Brackets Made of Premium Heavy Duty Alloy Steel. Corner Steel 4X4X3.5 Black 4 PCS is up for auction in Tools & Home Improvement. The current bid is $6.00, 85% below the $39.99 MSRP, in Good Condition. This auction has ended — similar items appear in live auctions regularly.