This is meant to be incorporated in larger things. Say you're printing a device enclosure and you want it to have an ethernet port, or you just want to use RJ-45 as a convenient 8 pin connector. Add this to your design and you can use the modular RJ-45 jacks sold at hardware stores that are meant to clip into wall plates.

Updated: Tightened the opening to clip more securely, cleaned up the openscad code, and made the whole thing a module to more facilitate use in other designs. Now jacks clip in so tightly that its hard to get them out again.