A distribution of the cooling air through one or more perforated tiles or other open areas in the raised floor of the data room is customized by placing one or more magnetic blocking tiles in a pattern to lie on top of the one or more of the perforated floor tiles or other open areas. The cooling air flow through the perforated floor tiles or other open areas to areas where the computing systems are not installed is cut off; and thus, the air flow is directed flow areas in the datacenter where the computing systems are designed to be located and actually are installed in the datacenter. The magnetic blocking tiles have a top surface that is solid and a bottom surface. The magnetic blocking tiles adhere magnetically to either the raised floor or the perforated tiles.