Those of you who are guitarists know what a capo is. Those of you who don't, it's a device that attaches to your guitar's fretboard and presses down on the strings, for the purpose of changing the key. This is sometimes useful for accompanying, say, a singer who sings in a key that is difficult to play on the guitar. Sometimes this is used for effect. When George Harrison plays "Here Comes the Sun," his guitar is in standard tuning, but he has a capo on the seventh fret, which is what gives it that tinkly sound ...
Um. Anyway, there are many brands of these. One of the most interesting ones I've found is made by a British firm, G7th, Ltd.
The original model was designed for steel-string acoustic guitars and works very well for them.
But since classical guitars generally have wider necks, and flat fretboards, the application of the G7th was somewhat limited. It could not be used past the fifth fret because it wouldn't reach across all six strings. (In the capo picture, the original is on the left, above.)
To attend to this, G7th has come out with a classical model (also a new one for twelve string guitars, which have wider fretboards.) The compression arm is longer, and the pad that presses upon the strings is flat. (The capo on the right.)
It works very well on a classical guitar, as far up as you can put it before you run into the thickening where the heel joins the neck to the body.
Plus, it looks so cool. You can see what it looks like on the guitar.
How it works is simple: You apply it by sliding it over the fret you want, and squeezing it shut. There is this wonderful little cam that locks it into place however hard you want it, and when you want to take it off, you just thumb the little lever down to open the jaws.
First-rate materials and construction, too.