TL;DR
A lag screw is a heavy hex-head wood screw, 1/4 inch in diameter and up, that draws structural connections tight as its coarse thread bites deep into solid lumber, installed in a pre-drilled pilot hole and driven with a wrench or impact driver. Classic uses include ledger boards, swing sets, pergola hardware, and TV mounts into studs, with washers spreading the clamping load.
What it means
A lag screw is a heavy hex-head wood screw, 1/4 inch in diameter and up, that draws structural connections tight as its coarse thread bites deep into solid lumber, installed in a pre-drilled pilot hole and driven with a wrench or impact driver. Classic uses include ledger boards, swing sets, pergola hardware, and TV mounts into studs, with washers spreading the clamping load. Modern engineered structural screws are displacing it because they install without pilot holes and carry published ratings, but the term persists for any large pointed fastener wrenched into wood.
Where it sits in the glossary
Lag screw is part of the Trade jargon group inside the ProFix Directory glossary. Browse every term in this category from the glossary index.
Why Ohio homeowners should know it
This is a term Ohio homeowners encounter when reading contractor quotes, hiring paperwork, or inspection reports. Understanding it well enough to ask one good follow-up question is usually all the protection a homeowner needs.
ProFix Directory keeps definitions short on the index page and saves the longer context — Ohio-specific rules, where the term comes from, and which ProFix tools touch it — for these per-term pages so the term is easy to cite and easy to share.
ProFix tools that touch this term
See also
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