This was the product that got it all started for us back in 1974, and to this day it's STILL the only fifth string capo worth putting on a banjo. It operates on a lever principle, not a spring, so it provides sufficient pressure to fret the string without muting the tone. It slides on a slim, dovetailed bar which mounts flush to the neck, making it sturdy and unobtrusive. 

View this link for correct capo Installation. 5th String Capo Installation Guide Pdf.