The humble guitar capo is an essential accessory that no guitarist should be without. This simple device allows you to play in a different key whilst still playing the same chord shapes.
A capo is a device that clamps down on a particular fret across the guitar's fretboard. It works by shortening the overall length of all the guitar strings at the same time, essentially moving the position of the nut. This means a capo can be used to alter the key of your guitar, which is particularly useful if you're a singer-songwriter and need to match the guitar to your vocal range. Another common use for a capo is to allow you to perform a song in a different key without needing to re-learn chord positions/shapes etc.