Tubular structure

Claim 1

A TUBULAR STRUCTURE COMPRISING TWO SUBSTANTIALLY INFLEXIBLE, DUPLICATE RIGHT ANGLED UNITS OF EQUAL LENGTH EACH CONSISTING OF ONLY TWO ELONGATED BASE WALLS OF UNIFORM THICKNESS JOINED TOGETHER LONGITUDINALLY IN RIGHT ANGLED RELATION, A FLANGE INTURNED ALONG THE FREE LONGITUDINAL EDGE OF THE FIRST BASE WALL AND DOUBLE BENT TO PROVIDE A LIP SPACED THEREFROM AND DEFINING THEREWITH A FIRST CHANNEL, THE CHANNEL BEING FACED TOWARD THE SECOND BASE WALL, AND A U-WALL HAVING A LEG DISPOSED NORMALLY OF THE SECOND BASE WALL AND FIXEDLY SECURED THERETO AT A POINT REMOTE FROM ITS FREE LONGITUDINAL EDGE, SAID U-WALL INCLUDING A RELATIVELY SHORT LIP INSET FROM THE FREE LONGITUDINAL EDGE OF THE SECOND BASE WALL BY A DISTANCE SUBSTANTIALLY EQUAL TO THE THICKNESS THEREOF, THE LIP BEING SPACED FROM THE LEG AND TERMINATING SHORT OF THE SECOND BASE WALL BY A DISTANCE SUBSTANTIALLY EQUAL TO THE THICKNESS THEREOF TO FORM THEREWITH AND WITH THE LEG A SECOND CHANNEL HAVING A LATERAL OPENING THEREINTO ADJACENT THE SECOND BASE WALL AND FACING AWAY FROM THE FIRST BASE WALL, THE TWO ANGLED UNITS AND THE TWO CHANNELS THUS FORMED BEING COMPLEMENTARY TO PERMIT THE LIP OF THE FIRST CHANNEL TO FIT SLIDINGLY WITHIN THE SECOND CHANNEL, AND VICE VERSA, WHEREBY THE TWO ANGLED UNITS ARE INTERLOCKED TOGETHER TO FORM A RECTANGULAR TAUBULAR STRUCTURE HAVING FOUR UNIPLANAR SIDES WITH TWO EXPOSED SEAMS ADJACENT DIAGONALLY OPPOSITE CORNERS THEREOF.