page_title: Truss rod
section_title: Location and adjustment
hierarchical_section_title: Truss rod / Location and adjustment
caption_attribution_description: English: Adjustment bolt for the truss rod of a Tanglewood Earth 200 acoustic guitar, visible through the sound hole.
context_page_description: The truss rod is component of a guitar or other stringed instruments that stabilizes the lengthwise forward curvature, of the neck. Usually it is a steel bar or rod that runs inside the neck, beneath the fingerboard. Some are non-adjustable, but most modern truss rods have a nut at one or both ends that adjusts its tension. The first truss rod patent was applied for by Thaddeus McHugh, an employee of the Gibson company, in 1921, though the idea of a "truss rod" appears in patents as early as 1908.
context_section_description: The truss rod tension is usually controlled using an adjustment bolt (a hex nut or allen key). Depending on the model of guitar, this bolt can be located:
  On older Fender-style electric guitars with bolt-on necks (and vintage re-issues) — on the heel of the neck. Adjustment of such truss rods can be done by a Phillips screwdriver and requires prior removal of the guitar's pickguard or neck.
  On newer Fender-style electric guitars — behind the nut, uncovered and can usually be adjusted by a 1/8" (3 mm) Allen wrench.
  On Fender American Elite Series — an adjustment wheel at the base of the neck on the top of the instrument.
  On set-neck electrics — under a cover-plate behind the nut. Gibson & Epiphone guitars have their truss rod bolt covered with a signature bell-shaped plate. Most Gibson electrics have a 5/16” (8 mm) or a 1/4" (6 mm) hex adjustable truss rod nut that can be adjusted with a hex box spanner wrench.
  On acoustic guitars — inside the guitar body, accessible through the sound hole, or on the headstock. Martins use a 3/16" (5 mm) Allen wrench and Gibson uses the same as for the Gibson electrics above.
  Modern designs also include adjustment from the side of the heel of a bolt-on neck. When looking from the body of the guitar to the head, counterclockwise adjustment decreases the truss rod tension (correct an underbow) and clockwise adjustment increases the truss rod tension (correct an overbow).
  Installing a truss rod in a newly constructed guitar requires woodworking capabilities.  Special tools are required including a router with a variety of bits and ability to work with metals.  Completed truss rods can be purchased through suppliers or manufactured according to specifications given in literature.
caption: Adjustment bolt visible through the sound hole.
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