Capo for Classical Guitar

The Dunlop ™ Toggle Action capo was designed for guitars with a flat touch. This capo is very easy to use and does not damage your guitar. Its highly contoured design allows you all styles of play, without any hindrance to the positioning of your fingers.

The professional version allows adjustment of the strap to fully fit the shape of your sleeve. A capo (often abbreviated as "capo") is a system used to transpose the neck of a stringed instrument without affecting tuning but limiting the use of strings to a smaller part of the neck.
The ropes are pressed against the handle (as in the case of a "barred").
The empty length of the strings becomes shorter, resulting in higher pitched sounds.

Source: Wikipedia