These parts can help you to pass a RJ45 thru a rack full of tangled cables. Put the connector into the guide with the tab facing the guide. You can pass a cord with a knot thru the tail hole of the guide to pull the cable with the cord, you can also pass a threaded stick with nuts and push it from back to front of the rack, or you can put the trailing connector in the guide to avoid breaking or trapping the tab between other cables when it's pulled backwards. I've created the part for two sizes of connector. Use the one that fits more tight.