The Simpson Strong-Tie TBP1475R50 TB Wood-To-Steel Screws are an ideal fastener for wood-to-hot-rolled steel fastening applications. They have a recommended thickness of up to 1/4". The flat head with nibs allows for easy countersinking. The TB structural screws feature a #3 square drive. A driver bit is included with each box of fasteners (replacement bit model BIT3S-2-R2). The black phosphate coating is recommended for dry, interior, and noncorrosive environments only. Common applications include fastening wood-to-steel truck beds, trailer flooring, and nailers and ledgers.