FlatLOK Structural Wood Screw

FlatLOK is a multi-purpose structural wood screw that can be used for fastening multi-ply LVL and girder trusses. The flat head allows for easy finishing including drywall or trim.

FlatLOK is approved for single-sided installation making the job easier to complete both at ground level or for elevated applications.

The FlatLOK wood screw features a TORX® ttap® drive system that maximizes bit fit, reducing the potential for stripping. The stability button allows for maximum penetration into the fastener and a wobble-free drive. A free TORX ttap bit is included in every box.


  • 2 7/8”: 2-ply roof girder trusses and 2-ply dimensional wood headers
  • 3 1/2": 2-ply LVL beams
  • 4”: Interior corridor ledgers
  • 4 1/2”: 3-ply roof girder trusses and 3-ply beams
  • 5”: 3-ply LVL beams
  • 6": 4-ply roof girder trusses and 2-ply open web floor trusses
  • 6 3/4": 4-ply LVL beams

FlatLOK is tested and supported by engineering data that conforms to the most current ICC standards. It is also approved for use in ACQ or treated lumber. For FlatLOK technical information, see the Technical Docs section below. For technical documentation of all our structural wood screws, see our Technical Resources page.


FlatLOK Structural Wood Screw

Learn how the FlatLOK Flathead Structural Wood Screw replaces nails and through bolts when attaching multi-ply LVL, dimensional beams and girder trusses. 

  • Sku Selections
  • Installation
  • Technical Docs
  • Purchase FM Products
FlatLOK SKU Selection Guide
 2 7/8"   2-Ply Roof Girder Trusses   2-Ply Dimensional Wood Headers  50 pc box  FMFL278-50
 500 pc bucket  FMFL278B-500
 3 1/2"   2-Ply LVL Beams   Built up Headers and Stair Stringers  50 pc box  FMFL312-50
 250 pc bucket  FMFL312B-250
 4"   Interior Corridor Ledgers   Built up Headers and Stair Stringers  50 pc box  FMFL004-50
 250 pc bucket  FMFL004B-250
 4 1/2"   3-Ply Roof Girder Trusses   3-Ply Dimensional Wood Headers  50 pc box  FMFL412-50
 250 pc bucket  FMFL412B-250
 5"   3-Ply LVL Beams   2x and 4x  50 pc box  FMFL005-50
 250 pc bucket  FMFL005B-250
 6"   4-Ply Roof Girder Trusses   4-Ply Dimensional Wood Headers  50 pc box  FMFL006-50
 250 pc bucket  FMFL006B-250
 6 3/4"   4-Ply LVL Beams   2x4x2  50 pc box  FMFL634-50
 200 pc bucket  FMFL634B-200


FlatLOK should be installed using an impact driver or high torque 1/2" variable speed drill (minimum 18V if cordless). No predrilling is required when properly installed. Bring fastener flush with wood surface, do not overdrive.

LVL Beams: Refer to FastenMaster's online technical bulletins and engineered wood manufacturer's technical information for complete load and engineering requirements.

For applications other than those listed above, a Professional Engineer (PE) may be consulted to determine proper connection design.

Technical Evaluation Reports (TERs)

TERs qualify for building official approval and are developed from test reports that comply with IBC Section 104.11.1

Technical Bulletins

FastenMaster technical bulletins are abridged versions of our TERs that demonstrate general guidelines and fastening patterns.

FlatLOK Technical Bulletin

FlatLOK Technical Bulletin - Canadian Version

This file contains the FlatLOK Technical Bulletin for Canada in both English and French

DWG Drawings

For use in CAD software

Catalog Pages

Product specific pages from our FastenMaster catalog.

Code Compliance Reports

Code Compliance Reports by State

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