1) Locked by butterfly hole structure and cargo dead weight, layer bearing capacity than type I (A) 2) Easy assembly and disassembly; limitless connection to main auxiliary rack; enhanced rack robustness 3) Save investment; layer plates arbitrarily adjustable at 75mm steps; steel, wood and other layer plates can be used 4) Rack consists of column disc, crossbeams, layer plates, safety pins and plastic footing.