FastenMaster FMFL312-50 FlatLOK 3 1/2" – 50 pc box is a purpose-built structural wood screw engineered to simplify heavy-duty framing tasks. Designed to work with multi-ply LVL and girder trusses, this fastener delivers dependable connections where strength and finish matter most.

The FlatLOK design features a flat head that tucks flush as you drive, making it ideal for applications that require a clean, paint-ready surface. Bed the screw into structural members with confidence, knowing that trim and drywall joints can be finished smoothly over the fastener head.

Single-sided installation is a hallmark of FlatLOK, enabling efficient work from ground level or elevated positions. This practical feature reduces the need to access the opposite side of the joint, speeding up installation on tall framework or tight spaces without compromising performance.

Key benefits

• Rotatable fit for LVL and girder trusses: optimized for securing multi-ply LVL assemblies and structural girders where reliability is critical.
• Flush, finish-friendly head: flat head designed to sit nearly flush for easy drywall and trim finishing.
• Efficient single-sided installation: simplifies work from one accessible side, saving time on ground-level and elevated projects.
• Bundled in a 50-piece box: ready-to-build quantity for mid-sized jobs, keeping downtime to a minimum.
• Clear, purpose-driven performance: a multipurpose structural wood screw that replaces multiple fastener types in compatible framing scenarios.

Ideal use cases

Use the FMFL312-50 FlatLOK screws when you’re assembling LVL members or securing girder trusses within structural framing. They’re well-suited for projects where a strong, one-side installation is advantageous and where a flush finish around the screw is desirable for drywall or trim work.

Who should consider this screw

Professionals and serious DIYers alike who regularly work with LVL and engineered wood products will appreciate the combination of long reach, flush finishing capability, and convenient single-sided installation. It’s a practical choice for carpenters, remodelers, and framing crews tackling mid- to large-scale projects where reliable fasteners and finish-ready results matter.

In short, the FastenMaster FMFL312-50 FlatLOK 3 1/2" – 50 pc box delivers a specialized, finish-friendly solution for secure, efficient connections in LVL and girder framing, with the convenience of a single-sided installation and a box size tailored to substantive jobs.