Steel pipe is an inherently efficient structural component. It combines strength with lightness and has no projecting corners. It is inexpensive and can be obtained in a wide range of sizes and thickness. The difficulty arises in joining pipe to form structures. Threaded pipe must be supplied in set lengths and is therefore relatively expensive and inflexible in application. Welding is labor intensive and requires a highly skilled workforce. The answer is provided by Viking Alexander clamps which has become the basis of a rigid tubular construction sytem proven time after time. The underlying principle is simple but highly effective a slip on fitting that can be used to create versatile and rigid tubular structures.