Fabricated structure there is more than fifteen years for Mobiltech ASD.

Links to male-female screeds and equipped with a safety pin.

Advantages:
-The upper cover can rotate and thread can "catch up arrow" under load.
-Easy assembly and disassembly without forcing and without tools.
Very high-speed assembly and disassembly.

Disadvantages:
Light-game assembly, and thus all of the beam is not really rigid. Can generate in certain configurations if efforts are alternated.
-Do is manufactured for a long time and it became difficult to purchase credit.

As against this can be found cheap used.