Model # FMHLGM412-12

Internet #202268269

Store SKU #517046

Store SO SKU #336802

FastenMaster HeadLok 4-1/2 in. Heavy Duty Flathead Fastener - (12-Pack)


HeadLok 4-1/2 in. Heavy Duty Flathead Fastener - (12-Pack)

$1249 /each

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Product Overview

Save time, money and labor costs! HeadLok eliminates the need to predrill and hand-ratchet in 3/8 in. galvanized lag screws in wood-to-wood projects. HeadLoks aggressive threading and sharp gimlet point allows it to zip right into wood or OSB without pre-drilling. Plus, the wafer head eliminates the need for washers and offers increased pull through strength. Perfect for deck framing, stair stringers, fencing, cabinets, and more! Sizes are perfect for virtually any dimensional wood-to-wood project.

  • Nationally code compliant. Stronger design shear values than 3/8 in. lag screws
  • No pre-drilling. Zip right in
  • Patented spider drive virtually eliminates cam-out
  • Guaranteed corrosion resistance for the life of the project. ACQ approved
  • Free spider driver bit in every package
  • American made

Info & Guides

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Assembled Depth (in.)
.189 in
Assembled Height (in.)
4.5 in
Assembled Width (in.)
.189 in
Screw Length
4-1/2 in


ACQ Rated Fastener
Drive Style
Driver bit included
Fastener Callout Size
4 1/2"
Fastener Plating
Fastener Thread Type
Fastener Type
Specialty Fastener
Fastener/Connector Material
Finish Family
Head Style
Measurement Standard
Package Quantity
Primary Use
Wood-to-wood construction i.e. decking, cabinets, stair stringers, SIP pannels, and more!
Product Weight (lb.)
Self drilling
Self tapping
Tamper Resistant

Warranty / Certifications

Manufacturer Warranty
FastenMaster fully guarantees HeadLok against rusting or streaking for the lifetime of the project. Please see the following link for further details at:

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Customer Questions & Answers

What is shear strength

Asked by: mike
Hi Mike - shear strength is a measure of force required to shear this screw perpendicular to the long axis. If you put this screw in a vice sticking straight up & down in the jaws, put a pair of pliers on it right above the vice jaws, and applied force horizontally 'til the the top part of the screw separated from the part held in the vice, the force you applied was the screw's shear strength. As the screw appears to be less than 3/8 " in diameter but is claimed to be stronger in shear than a 3/8" lag bolt, it must be made of hardened steel, stronger than standard mild steel. MIld steel has a tensional strength of about 60,000 lbs/sq in; an often used engineering assumption is that the shear strength is greater than 1/2 of the tensional strength, or about 30,000 lbs/sq in. For a 3/8" lag bolt, the shear strength will be (very roughly) 30,000 * 0.11 = 3300 lbs., where the 0.11 is the cross-sectional area of the 3/8" screw in sq inches. This is a very rough number, should be used for any safety calculations.
Answered by: EfRed
Date published: 2017-05-28

Thread diameter?

Asked by: Tina

Im building a dock on a lake using treated pine. Im using 2x 6,8, and 2x 12....Post are 4x4, W...

Im building a dock on a lake using treated pine. Im using 2x 6,8, and 2x 12....Post are 4x4, What size screws should i use or should I use nails?
Asked by: roger
  • y_2017, m_7, d_24, h_23CST
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Customer Reviews

HeadLok 4-1/2 in. Heavy Duty Flathead Fastener - (12-Pack) is rated 4.0 out of 5 by 6.
Rated 1 out of 5 by from Terrible Customer Service Bought a box of the 2 7/8" screws for a home project The first five I used were so dull that even with a fresh battery in my driver, I had to predrill every hole. Then I almost tore my hand to shreds with a damaged screw head. Complaints onlon line went unanswered. BUYER BEWARE!!
Date published: 2017-04-17
Rated 5 out of 5 by from Homemade Camper Project These screws are advertised as being stronger than regular lag bolts. I purchased these in two different lengths for use in my project. I already had a partial box of these in 6" length from a previous project. I find that pre drilling a pilot hole before installing is the best way to go in the Douglas Fir I am using. I especially like the fact that an installation tool is provided with each box of screws. The screws have an aggressive thread which provides a great grip into lumber. Holding power is what I wanted and I believe these screws provide just that.
Date published: 2016-02-23
Rated 5 out of 5 by from This product is versatile, strong and virtually invisible The HeadLok line of fasteners from Fastenmaster provides utility and ease of use. We use them all over for decks, railings and shade structures.
Date published: 2013-08-21
Rated 5 out of 5 by from Great product. Warrantied for life of project. I will periodically inspect corrosion protection. Saves time. Saves money in bulk. No need for rafter hangers. Corrosion resistant for life. Great product.
Date published: 2015-08-25
Rated 5 out of 5 by from Super screws home depot had these screws cheaper than anyone else online. these scews are excellent for all application that supper hold is needed and isnt seen or cosmetic isnt a issue they have large heads they are stronger than most lag bolts easily installed with my 14v cordless
Date published: 2011-05-02
Rated 3 out of 5 by from great screw, lousy bits I love the screws. They drive easily into PT timbers with impact drivers. The bits however are way too soft and self-destruct very easily. I went through 13 spider bits for only 150 screws. So if you buy a bucket load of screws, be prepared to buy all of the spider bits available in the store. I used two impact drivers for this particular job. The first was a Milwaukee 2563 cordless impact driver with 3 torque setting options. To drive the 4.5 inch screw, the most powerful setting was needed. It would come close to flush driving the screws in PT timbers and boards. The only problem was the battery would die after only a dozen screws. So I don't recommend using that tool with this size screw. The second impact driver was a Porter Cable 120v driver. It had no problem power wise and would easily drive the screws. The only concern is it does not have any torque setting options. So you have to be careful when driving to stop before the head gets close to being set how you like or need it to be. I'm looking for a 120v impact driver with torque settings. That or another cordless impact driver with torque settings and more power or larger battery capacity. Again, love the screws, hate the spider bits.
Date published: 2013-06-23
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