The Third Hand Capo is essentially unchanged since 1976. It is still hand-made in the USA, and has passed all tests of time & durability and has proven to fit virtually all guitars without damaging them or coming apart.
The elastic strap, though not fashionable these days (it was state of the art for capos in 1975) applies enough pressure even for 12-string guitars, lasts for years (and is easily replaced) and distributes the force evenly around all the various types of guitar necks. The Third Hand comes with detailed instructions, making it the only partial capo that offers you any real information about how to use it to play music. All the other brands of partial capos, including Shubb, Kyser, SpiderCapo and Woodie's for some reason offer almost no information about where to put the capo or your fingers.
There is only one model of the Third Hand capo. The 2012 capos have a dark brown stripe in the elastic and not the red shown in the photo.) The pin is long enough to accomodate classical guitars and 12-strings (including 2" fingerboards) and the discs are high enough to handle even high-action guitars. It can be used on a ukelele, mandolin, bouzouki, mandocello or banjo by removing discs. (You will probably want to saw off the pin if you do this. The brass cuts easily with even a Swiss Army knife hacksaw blade.)
Spread the hard rubber discs apart along the solid brass pin by hand to match the spacing of your strings. Then place the white nylon "side-support" on whichever side of the fingerboard works the best (if you are only capo-ing a few strings, this matters for stability.) The discs do not move on the pin, even if you drop the capo, and you can take it on and off your guitar and put it in the case and it will still be adjusted in the same configuration you left it in and ready to pop right on the guitar for the next time you use it. If you have a guitar with a very curved fingerboard (such as a Fender electric), you can even remove the rubber discs and bend the pin a little. You may not be able to attach it at the 12th fret of a classical guitar or other 12-fret necks with large neck heels, and you will find it is not easy to reach over it or around it. When you do reach over it, you will generally not move the discs around so as to require re-seating them. You can remove some discs to improve access to notes under and behind it.
When you move it from the 2nd fret to the 7th fret, for example, you generally need to space the discs apart wider, because most guitars get wider as you go up the neck. If you are constantly switching the capo from fret 2 to fret 7, you might want to have 2 of them to avoid making this adjustment all the time.
The Third Hand took me 9 seconds to change configurations and put on, and only 6 seconds to move up 2 frets. When I took it off, set it down, and put it back on, it took only 4 seconds. (It takes me 2 seconds to put on a Shubb Esus capo.) This is a real issue for a performer- if you set the SpiderCapo capo in place, play a song, then take it off and put in on a few songs later, it will need to be carefully re-seated the second time. This might prove to be a problem when you are nervous at a big gig, in poor stage lighting, or after a few beers. It is also possible when reaching over the Spidercapo to accidentally knock the levers out of position in such a way that they will lose their grip and they will need a quick re-adjustment.
I have stepped on a Third Hand Capo, and they don't break. The elastic wears out after a few years, but can be replaced for a few $. The pin, discs and nylon side-support last essentially forever.
The Spider Capo (which they insist on spelling SpiderCapo) appeared in 2008, and though it has a more "space-age" look than the Third Hand, it basically does the same musical things as the Third Hand. The SpiderCapo basically does the same thing as the Third Hand. It can clamp all 63 combinations of partial capo at any fret on almost any guitar, and like the Third Hand it blocks easy access to notes under and behind the capo. It is made in China, of plastic that looks like gun-metal, and appears to not harm the guitar or have any parts that will wear out. At the crucial places where the clamp mechanism grips the side of the fingerboard there are glued pieces of soft ox leather that protect the guitar from the force of the clamp.
The SpiderCapo comes with very little useful information about where to put the capo or your fingers. Thousands of players for decades have failed to find most of the clever ways to get new music from a partial capo, and you probably won't find it either without some help.
The clamp mechanism applies force only laterally (no forces other than the tensile strength of the shaft are pushing the capo levers onto the strings), and the capo must be placed on the guitar with none of the "fingers" touching the strings, snugged against the fret & tightened. Then the "fingers" are spun into place with the levers, and they apply force onto the strings by pushing against the rigidity of the shaft which is tightly clamped to the fingerboard. (The earlier incarnations of the SpiderCapo used a softer plastic, and could not hold their grip on a medium gauge string being bent or flatpicked very hard. The newer SpiderCapos seems to have solved this problem, and they are much more robust and now hold firmly on medium gauge strings.)
The "fingers" on the SpiderCapo spin more freely on the pin shaft than the Third Hand, and can be bumped out of place, requiring them to be carefully re-positioned each time you take the capo off and put it back on again. Even to slide it up a couple frets requires quite a bit of maneuvering, because the "fingers" move around and because the threads on the clamp are quite fine it takes a lot of unscrewing (5 turns) to take it off and put it on again. It took me 27 seconds to take one that I pulled out of a box of capos and put it into an Esus shape on a guitar. It took me 35 seconds to move it up 2 frets once it was on the guitar, (and 20 seconds on the 2nd try) since you have to flip the levers up, clamp the capo, then spin them back down. It seems like they should stay in place when you move it 2 frets, but they don't. After I took off the SpiderCapo, it took 17 seconds to put it back on in Esus position.
It remains to be seen if the thread clamp mechanism is strong enough to crack the binding or damage the finish on bound fingerboards, since it must be tightened a lot to hold its grip on an acoustic guitar that is being played with a lot of force. The "fingers" can be spun up or down in the middle of a song, without removing the capo, which offers some advantages, and is a unique feature of the SpiderCapo. On my guitar with medium gauge steel strings, to switch between Esus (0 2 2 2 0 0 ) and Open A (0 0 2 2 2 0) throws off the tuning of the B string enough to require a tuning adjustment, somewhat nullifying the usefulness of this feature. This is less of a problem on electric or nylon string guitars, and many of you out there may be able to spin the "fingers" up and down without throwing off your tuning.
Because the SpiderCapo does not wrap around the neck, it can also be attached very high on the fingerboard, including at the 12th fret of a classical guitar, and has no trouble even with massive necks on National guitars etc. As you move it up the neck, just as with the Third Hand, the "fingers" also need to be re-spaced to match the widening string spacing.
I have never stepped on a SpiderCapo, and don't know if it would break if I did.
The SpiderCapo cannot handle the double strings on a 12-string, and there are 2 other models: The XXL intended for wide neck guitars (and 7 or 8-string) and the Mini is for ukeleles, banjos or mandolins. We have them both in stock.