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