Definition

Noun: A type of fastener with a smooth, rounded head and a square section beneath the head. The bolt is partially threaded along its shank and is designed to be used with wood. When tightened, the square section pulls into the wood to prevent the bolt from spinning.

Usage

A carriage bolt is specifically designed for joining wood to wood or wood to metal. The square section under the head requires a pre-drilled hole. As the nut is tightened on the threaded end, the square section embeds itself into the wood, locking the bolt in place so it cannot turn.

Examples

• The deck was securely fastened using carriage bolts and heavy-duty nuts.
• For the timber frame construction, you will need to drill a hole slightly larger than the shank before inserting the carriage bolt.
• The rounded head of the carriage bolt provides a finished look that is safer and more attractive than a standard hex bolt.

Advanced Usage

• "Through-bolt" application: A carriage bolt is often used as a through-bolt, meaning it passes completely through the materials being joined, with a nut fastened on the opposite end.
• Anti-rotation feature: The key functional aspect is its self-locking, anti-rotation design, which eliminates the need to hold the bolt head with a wrench during assembly.

Variants and Related Words

• Coach bolt: A common synonym for "carriage bolt," used frequently in British English.
• Round head square neck bolt: A more technical descriptive name for this fastener.

Synonyms

• Coach bolt
• Round head bolt (though this is a broader category that may not always have the square neck)

Related Phrases/Idioms

• "Bolted down": While not exclusive to carriage bolts, this phrase meaning "secured firmly" describes their primary function.
  • The structural beams were bolted down securely with large carriage bolts.

Noun

1. a roundheaded bolt for timber; threaded along part of the shank; inserted into holes already drilled