I installed them on my Charvel Model DS-2 ST. I unscrewed the old Strap locks. The New Screws were just a little bigger. I put some Soap on the Screw Tip. And had no Problem Screwing on the New Screw to the Guitar Body. Tighten Down Firm. I also put on new Felt Washer made by Fender which I bought on Amazon too.  I installed the Reliece Part on a Walker & Williams Learher Strap. Went on with no Problem. Just used a Neddle noise Plyers to clip the Supplied Clip on.  Great Guitar Locking Strap.