I have a bar grate I modeled. It is made from 3/16 x 1" bars set at 1 3/16 OC.  When I look at the mass I get the mass for the entire VOLUME.  Grating 36" x 43" x 1" plain carbon steel is  525 POUNDS!! NOT!  That is the weight if the entire volume was steel.  How do I get the correct weight?

Thanks