Specification - T1100-F - Frame and Grate Systems MIFAB series T1100-F-4 6in wide steel frame and grate system. Lacquered 3/4in x 3/4in x 1/8in welded angle iron steel frame with anchor tabs located every 20in for anchoring support. Standard 20in long ANSI rated "Special Duty" lacquered ductile iron heel proof grates with a safe live load of over 10,000 lbs.