... as end bar).WT3: welding fixing stair tread with front chequered plate nosing.WT4: bolt fastening stair ... centers15-30, 40, 60, 80, 90 mm etc. with 30, 40 mm recommended.Cross bar centersany greater than ... 30mm is ok. with 50, 100mm recommended. Surface treatmentG-hot-dip galvanization(G ... tread,teeth steel grid,serrated steel stairs,anti skid steel steps