Swage locked grating is also called aluminum grating, because it's mainly made of aluminum steel bars. Other materials can be stainless steel bars. The cross bars are inserted into pre-punched holes of bearing bars and then it is hydraulically swaged under tons of pressure to lock the bearing bars in place. There are three kinds of bearing bars: rectangular bars, T bars or I bars. I bar swage-locked grating is lighter and cheaper than the rectangular bars swage-locked grating, and is the most widely used type. And now the close mesh steel grating is also available of 7/16" to 11/16" bearing bar spacing for special uses.