total categories   -Steel case board    |-Standard type    |-Opposite card type    |-Half Card type    |-Perforation type    |-Inclined card type    |-I type   -Al material grid   -Groove cap    |-TG type    |-TU type    |-TGD type    |-Hing sump grates and frames    |-Manhole cover    |-Cable trench covers   -Steel ladder    |-Inclined ladder     |-A type     |-B type    |-Upright ladder   -Step   -Handrail    |-Light    |-Heavy    |-Super heavy   -Enclosure   -Others   -Sorts of material surface processing   -Engineering practice