A clamp for preventing the slippage of the strings of a guitar over the nut thereof comprises a plurality of blocks between which are disposed the strings of the instrument. A bolt passes through the blocks and is threaded into the end one thereof. Tightening of the bolt drives the blocks together causing the strings to become clamped therebetween. Means is provided for retaining the handle on the bolt in such a manner that it cannot fall off through casual handling and may be selectively reoriented on the bolt so as to obtain the optimum axial orientation of the handle on bolt when the handle is in the fully clamped position. The spacers may be formed as cylindrical members with a flattened side or a key groove.
