5/16 in. x 3 in. Zinc Carriage Bolts (100-Pack)

Zinc-plated steel carriage bolts designed for fastening wood to wood or metal while providing a smooth, low-profile dome head finish. The square shoulder locks into the material to prevent spinning during tightening, delivering a clean, secure install for decks, fences, carts, and general projects.

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Key Features:

• Zinc-Plated Protection: Resists rust and corrosion for durable indoor and light outdoor use
• Low-Profile Dome Head: Creates a smooth, snag-free surface ideal where clearance is limited
• Square Shoulder Lock: Grips the material to prevent bolt rotation—no washer needed under the head
• Multi-Material Use: Fastens wood to wood or wood to metal with reliable holding power
• Installation Tip: Pre-drill a hole matching the bolt diameter for best results

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Specifications Table:

Specification	Details
Bolt Diameter	5/16 in.
Length	3 in.
Thread Size	5/16-18 UNC
Material	Steel
Finish	Zinc-plated
Head Type	Dome (carriage) head
Shoulder	Square shoulder under head
Pack Quantity	100 pieces
Intended Use	Fasten wood to wood or wood to metal
Installation Recommendation	Pre-drill hole matching bolt diameter

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Frequently Asked Questions (FAQ):

Q: What materials can these carriage bolts fasten?
A: They are designed to fasten a wood face to either wood or metal.

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Q: Do I need a washer under the head?
A: No— the square shoulder seats in the material to prevent turning, eliminating the need for a washer under the head.

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Q: Are these suitable for outdoor use?
A: The zinc plating offers moderate corrosion resistance, suitable for indoor and some light outdoor applications; for harsh environments, consider stainless or hot-dip galvanized.

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Q: What drill size should I use?
A: Pre-drill a hole that matches the bolt diameter (5/16 in.) for proper fit.

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Q: What nuts are compatible?
A: Use 5/16 in.-18 coarse thread nuts and washers as needed on the nut side.

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A Clean, Domed Detail for Seamless Strength

The soft dome of this carriage bolt delivers a polished, unobtrusive accent—strength that disappears into the design. I love how the square shoulder locks in, keeping the head flush and refined on benches, gates, and utility carts. Pair it with zinc hardware for a cohesive, silvery sparkle that feels both functional and elevated. It’s the quiet essential that makes everyday builds feel luxe and intentional.

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Secure your next project with these zinc-plated carriage bolts—order the 100-pack and build with strength and a clean, low-profile finish.