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What's a shim and when do I need one?
A shim is a thin piece of material jammed in to correct an angle or fill a gap that's throwing off geometry somewhere in the guitar. Could be a sliver of wood, plastic, metal, or bone… even a piece of a shopper rewards card from your grocery store (ask me how I know). Unglamorous? Extremely. Also one of the most cost-effective fixes in the whole repair world, when it's actually the right tool.
Neck angle shims
The most common use, especially on bolt-on guitars (looking at you, Taylor). Instead of a full neck reset, a shim in the neck pocket changes the neck's angle relative to the body, raising or lowering string height at the bridge. This is exactly why bolt-on necks are so much cheaper and faster to fix than glued dovetail joints — you're adjusting geometry with a shim instead of steaming apart a decades-old glue joint like some kind of guitar archaeologist. (Curious what that steaming-apart process actually looks like? See Does my guitar need a neck reset?.)
Nut and saddle shims
Occasionally used to raise string height a touch, though a proper nut or saddle replacement, or reslotting, is almost always the better long-term move. A shim is more of a quick, less-invasive stopgap than a real fix. Now, that doesn’t mean I won’t reach for one when budgetary constraints make the real fix too expensive. Do what works, when you gotta.
When you actually need one
If your action is high at the bridge, your saddle's already low or maxed out, and the neck angle itself is the real problem — not a warped top or bridge issue — a shim (especially on bolt-on necks) can solve it without the cost or risk of a full neck reset.
The catch: shimming the wrong thing, or shimming to paper over a different underlying problem, just kicks the real issue further down the road. Get an actual measurement before assuming a shim is your answer.
Book Now for a free evaluation, and we'll find out what's actually going on before reaching for a shim.