RJ Lock - Nut replacement/Lock for Trailer Ball - Prevent Trailer Theft (Silver) Tow anything of Value? Secure your trailer with this patented lock that replaces the nut under the hitch-ball to protect against trailer theft. SEE PRODUCT DESCRIPTION BELOW FOR MORE DETAILS Remove the exiting nut on your trailer ball with a 1" shank, and secure the universally fit RJ Lock in its place. Easy installation. (The typical 1" shank has a 1 7/8", 2" or 2 5/16" ball. RJ Lock not currently made for 3/4" or 1 1/4" ball shanks.) Even with the receiver and coupler locks - you're unattended trailer equipment is not fully protected! This lock is the Missing Ling in trailer theft protection. Precision Made - Corrosion Resistant - Same thread count as a standard ball nut