Tremolo System Intonating Tool to set the intonation on bridges. Tighten the screw until it begins to grip. This ensures that the bridge saddle won't slip forward when you slacken its allen bolts. You can then adjust the intonation, tightening the tools knurled rings to move the saddle back if the string was sharp or slackening it to move the saddle forward if it was flat.
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