2009 Toyota FJ Cruiser Owners Manual - Page 213

2-5. Driving information Selecting trailer ball Use the correct trailer ball for your application. Trailer ball load rating Matches or exceeds the gross trailer weight rating of the trailer. Ball diameter Matches the size of the trailer coupler. Most couplers are stamped with the required trailer ball size. 2 When driving Shank length Protrudes beyond the bottom of the lock washer and nut at least 2 threads. Shank diameter Matches the ball mount hole diameter size. Connecting trailer lights Use the wire harness stored in the rear end underbody. 191