Shim

A thin piece of material inserted at a joint to change its angle or raise a component slightly.

In a guitar it appears in two common places: under the heel of a bolt-on neck, to change the neck angle so that the bridge can be adjusted into range, and under a nut, to raise the whole string set when the slots have been cut too deep. The material matters, since card compresses while a piece of wood or thin plastic holds its thickness. Because a shim changes geometry, it is always a correction for something else being slightly wrong.

Example: a full-pocket shim of thin veneer under a neck heel will lift the strings when a bridge has bottomed out.

Shim

See also