Home - Trailers - Trombones - Straight Frame Extendable Trombone Trailer Straight Frame Extendable Trombone Trailer Dennison’s Straight Frame Extendable Trombone Trailer comes complete with air operated locking pins and a Keruing hardwood floor as standard. Its ENXL certified headboard has been tested up to 17 tonnes. FEATURE AND BENEFIT SUMMARY Extends to 21.2 m when fully open – can be used for operating within standard C & U Regs or on special types for over-length, indivisible loads Air operated locking pins – includes 1500mm opening intervals for different load lengths ENXL certified fixed flush headboard – tested up to 17 tonnes Sockets and posts – for load safety and security Galvanised post trays – storage for posts when not in use 29mm Keruing flooring – durable and hard wearing