Instructions for this kit state that screw lock is included. It is not on the listing nor in the package. This product is a cheap knock-off from other higher end brands like DeeZee. The instructions seem to be detailed, but do not make the installation easy. I suggest watching a video of installing this set from another user or via a google search. I was able to install it after a trip to the auto parts store for thread blocking and after watching a 5 minute YouTube video. The manufacturer should review their instructions.