A couple different designs for devices that aid in leveling strings from below. One uses a counter weight (adjustable), the other uses a spring to press a piece of flat steel upward against the strings of a unison. It simply rests on the keybed, so it is using the keybed as its reference (making the strings parallel to the bed). Some keybeds have portions routed out, so you need to improvise something in that case to give a base of support. It is opposite from an above string level: you lift (or push up from below) the string(s) that are muted until all are equally muted.#understringlevel #stringlevel #UserTag1