Double bass 'C' Extension Capos, also known as chromatic latches, closers, or gates, attach to the fingered extension, giving the player added capability when playing the extended notes. By stopping a note on the extension with the Capo, the note temporarily becomes effectively an open string, and need not be stopped with a finger. This reduces much of the technical disadvantage associated with fingered extensions. Anzellotti Bass Capos offer an advantage over other 'C' extension closures in that they are easy to install and adjust compared to handmade latches, and they were carefully designed and engineered to maximize performance.