Instructional video
Attaching to the Modular Plug The RJ Patch Cord Lock works on patch cords that don't have a strain relief, as well as ones that do.
Attaching to a Strain Relief Patch Cord
Some strain relief patch cords have a boot. If you have one with a boot it needs to be cut off. Slide the lock over the cord. Insert the patch cord into the RJ45 Jack. Then slide the lock forward under the tab. Finally, tighten the center set screws down to secure the lock onto the strain relief.