The problem caused by the time consuming and potentially damaging process of applying a standard masking to the neck of a stringed instrument is solved by providing a strip of polymer material having slots formed therethrough and being complementarily configured to receive the frets while covering at least a portion of the neck to prevent damage to the neck in the fret filing process. Optionally, a non-permanent adhesive is provided on one side of the strip. This invention provides a fast means and method for applying a masking to a stringed instrument neck, that does not require a high level of expertise, while fully protecting the neck during the fret filing process.