The portable restroom transportation trailer from Johnny Mover Trailer Sales has a skid-locking system that secures multiple units using an iron bar locked into place with a chain binding system. Models are available to handle six to 20 restrooms, and all feature front deflectors to protect units from road spray and debris, brakes, paint options, lighting, and leaf-spring suspension, with optional powder coating and chrome wheels. 800/498-3000; www.cesspoolcleaners.com/johnny.html.