Compound steel grating is composed of checkered plate on sealed surface & steel grating with certain spanning capability. Compound steel grating is formed of any type of steel grating and checkered plate in different thicknesses. The type JG323/40/100, JG253/30/100 and JG323/60/100 are generally used as base & the checkered plate with 3mm thickness is used as sealing plate. Sometimes checkered plate with thickness of 4mm, 5mm or 6mm is also used as sealing plate according to customers’ requirements. As thermal stress may cause shape distortion after hot-dip galvanizing treatment, especially when choosing large spacing grating, it’s not easy to flatten. So special attention should be paid when choosing grating types.