From wikipedia:
Wood finish
When used as a wood finish, linseed oil dries slowly and shrinks little upon hardening. Linseed oil does not cover the surface as varnish does, but soaks into the (visible and microscopic) pores, leaving a shiny but not glossy surface that shows off the grain of the wood. A linseed oil finish is easily repaired, but it provides no significant barrier against scratching. Only wax finishes are less protective. Liquid water will penetrate a linseed oil finish in mere minutes and water vapour bypasses it almost completely.[4] Garden furniture treated with linseed oil may develop mildew. Oiled wood may be yellowish and is likely to darken with age.
Linseed oil is a traditional finish for gun stocks. A very fine finish may require months to obtain. Several coats of linseed oil is the traditional protective coating for the raw willow wood of cricket bats. Linseed oil is also often used by billiards or pool cue-makers cue shafts, as a lubricant/protectant for wooden recorders, and used in place of epoxy to seal modern wooden surfboards.
Additionally, a luthier may use linseed oil when reconditioning a guitar, mandolin, or other stringed instrument's fret board; lemon-scented mineral oil is commonly used for this purpose. It is desirable, after cleaning a fret board, to apply a light amount of linseed oil (or other drying oil) to protect it from grime that might otherwise result in accelerated deterioration of the wood.
