The Simpson Strong-Drive MTH Wood Underlayment Screw (Collated) - #7 x 1-1/4 in. Gray Phosphate is engineered by Simpson for fast and secure underlayment-to-subfloor installations. Unlike nails, its intricate high-low thread pattern holds underlayment tight to the subfloor to prevent pull-out and eliminate squeaking before it starts. The compact trim head sits flush at the surface, keeping floor coverings from settling into countersink recesses - delivering a clean, professional finish every time.

Key Features

• Trim head with nibs - countersinks easily and sits flush, so floor coverings lay flat without catching on recessed pockets
• #2 square drive - provides reliable torque transfer and reduces cam-out during high-volume installation
• Driver bit included in every box - the #2 square drive bit (model BIT2S) is ready to go right out of the box, saving a separate trip for accessories
• High-low threads - the alternating thread pattern locks underlayment firmly to the subfloor, resisting pull-out and preventing the movement that causes squeaky floors
• Sharp point - starts cleanly and penetrates quickly without pre-drilling, keeping the workflow moving
• Curved collation - compatible with the Simpson Strong-Tie Quik Drive PRO200SG2 auto-feed screw driving system, enabling faster, no-bend-and-kneel installation across large floor areas
• Gray phosphate coating - suited for dry, low-corrosion interior environments where underlayment and backer board installation typically takes place

Why This Product

• Engineered specifically to stop subfloor squeaks - the high-low thread design is purpose-built for underlayment fastening, gripping the subfloor in a way that standard nails or general-purpose screws cannot match, keeping the connection tight long after installation
• Flush, floor-covering-friendly finish - the compact trim head with nibs countersinks to a level surface, protecting tile, hardwood, vinyl, and other finish materials from telegraphing fastener locations or cracking over recessed voids
• Built for production-speed installation - curved collation pairs directly with the Simpson Strong-Tie Quik Drive PRO200SG2 auto-feed system, allowing installers to drive screws upright across large areas and dramatically reduce fatigue and installation time
• Everything needed to start is in the box - each pack includes a #2 square drive bit (model BIT2S), so the job can begin immediately without sourcing additional tooling

Specifications

• Model Number (MPN): HCKMTH114S
• Screw Size: #7
• Length: 1-1/4 in.
• Head Type: Trim Head
• Drive Type: #2 Square
• Thread Type: High/Low Threads
• Point Type: Sharp Point
• Collation Type: Curved
• Coating: Gray Phosphate Coating
• Compatible Tool: Simpson Strong-Tie Quik Drive PRO200SG2 auto-feed screw driving system or attachment
• Quantity: 1,000

Approved Applications

• Underlayment / Backer board installation to subfloor

What's Included

• #2 square drive bit (model BIT2S)

Frequently Asked Questions

What makes the MTH Underlayment screw better than nails for subfloor applications?

Unlike nails, the MTH Underlayment screw features an intricate high-low thread pattern specifically designed to prevent squeaking by holding underlayment tight to the subfloor and preventing pull-out, providing a more secure and long-lasting connection.

What tool is required to install these collated underlayment screws?

These screws install with the Simpson Strong-Tie Quik Drive PRO200SG2 auto-feed screw driving system or attachment, which is compatible with the curved collation strip format of these screws.

Are these screws suitable for wet or high-moisture environments?

No. The gray phosphate coating is recommended for dry, low-corrosion environments only. For installations in areas with higher moisture exposure, a different corrosion-resistant coating would be more appropriate.

Does this pack include a driver bit?

Yes. Each box includes a #2 square drive bit (model BIT2S) so you can get started right away. Replacement bits are available separately under model number BIT2S.

Note: Product dimensions and/or thread length may differ from picture. Please see the item description above for specifications.