There are different base material options for grating. Steel (stainless, powder coated, galvanized) and aluminum are popular and durable choices, but brass, bronze and even copper are available too. The bridge seen here is made with aluminum bar grating. The term “bar grating” is drawn from the small bars that make up each panel. The bars are welded or mechanically locked together at a regular interval by crossbars, and the spacing of each determines the overall transparency.