`HITCH-TITE` (use on receiver Models) is a simple method to ensure a no-slop hitch attachment A size specific metal sleeve w/a nut welded to inside of it; This metal sleeve then slides into base of rack. Line nut up w/ pre-drilled hole in base. Customer slides base into receiver hitch & uses special threaded hitch-pin included to tighten (Retro-Kit available). Included with all locking models e.g. Porter Hitch 4 Cycle On Pros and Axis Aluminum