LedgerLOK Flat Head Structural Wood Screw

LedgerLOK Flat Head is a code-compliant structural wood screw engineered to fasten a deck ledger board to the rim joist of a house with no predrilling. LedgerLOK replaces lag screws and through-bolts, has been coated with a proprietary three-step coating process that protects against corrosion (even in pressure treated wood) and is ACQ approved.

The built-in washer head eliminates the need for an additional washer, saving time and money. The LedgerLOK Flat Head with TORX® ttap® drive system installs flush to the ledger installation saving additional time and money.

All LedgerLOKs are guaranteed not to rust or corrode for the life of the project. The fasteners have also been tested and approved for use in ACQ including contact treatment levels. LedgerLOKs are not recommended for saltwater applications.

For LedgerLOK Flat Head technical information and drawings, see the Technical Docs section below. For technical documentation of all our structural wood screws, see our Technical Resources page.


LedgerLOK Flat Head Structural Wood Screw

LedgerLOK Fasteners are designed specifically for attaching a deck ledger to the house. The LedgerLOK Flat Head Fastener comes in two lengths – the traditional 3 5/8" is for single ledgers, and the 5" version for double ledgers and thicker applications. The LedgerLOK Flat Head includes two new features versus the original hex head design: a wide washer head that can be driven flush to the ledger surface, and the TORX TTAP Drive System.

  • Sku Selections
  • Installation
  • Technical Docs
  • Purchase FM Products
LedgerLOK Flat Head SKU Selection Guide
 3 5/8"   12 pc clamshell   FMLLF358-12
50 pc box FMLLF358-50
250 pc bucket FMLLF358B-250
 5"   12 pc clamshell   FMLLF005-12
50 pc box FMLLF005-50
250 pc bucket FMLLF005B-250


LedgerLOKs should be installed using an impact driver or high torque, 1⁄2" variable speed drill (at least 18V if cordless) or impact driver. Choose the proper length so that threads fully engage the main member (i.e., rim joist). Bring head flush with ledger using the flat head style. Not for use in masonry or concrete.

For detailed installation instructions, including fastening requirements, please refer to our Deck Ledger to Rim Joist technical bulletin. These instructions are included in all box and bucket packaging as well as being available for download from our website.

When using in non-ledger applications, a design professional should be consulted for all critical connections, which include the number and location of all fasteners to meet national and local code requirements.

ICC-ES Report, ESR 1078

The ICC-ES Evaluation Report demonstrates to the installer and code official that our LOK fasteners comply with the most current building codes. This report also provides the engineer with critical values needed to design safe installations. Reports from ICC-ES are the most recognized reports used by code officials across the U.S. This document can be shared with code officials, engineers, architects and specifiers who may have questions regarding proper use or code compliance of LOK fasteners.

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.

Deck Ledger to Rim Joist Technical Bulletin

This file contains the Deck Ledger to Rim Joist Technical Bulletin for Canada in both English and French

Deck Ledger to Rim Joist Technical Bulletin - Canadian Version

This file contains the Deck Ledger to Rim Joist Technical Bulletin for Canada in both English and French

DWG Drawings

For use in CAD software

Warranty Information

LedgerLOK Guarantee of Performance

This file contains information regarding LedgerLOK guarantee of performance.

Catalog Pages

Product specific pages from our FastenMaster catalog.

Code Compliance Reports

Code Compliance Reports by State

Purchase FastenMaster Products

To find a dealer near you, click below:

Find a Dealer