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You can purchase capos at music stores or online. There are three conventional capos that you can get for the first four frets of the banjo. These include the elastic, clamp, and screw capos. Compare the three different kinds of capos online and choose one that meets your needs and fits in your budget. Elastic capos are often the cheapest but least exact kind of capo. Clamp capos use a spring to create tension. Screw capos allow you to adjust the tension of the capo and are the most popular for banjos. A Shubb sliding capo is made specifically for banjos and can slide up and down the neck past the fourth fret. Shubb capos should be professionally installed by a luthier or banjo professional because they have to be screwed into the neck of the banjo. Railroad spikes are placed in holes that are punched into the frets under the fifth string and can be used as a capo for your fifth string. Take your banjo to a luthier or professional that works on musical string instruments so they can install it for you. Typically railroad spikes are installed between the seventh and tenth frets.
Get a traditional capo for the first four frets. Use a sliding capo for the fifth string. Get railroad spikes installed past the fourth fret.