Structural Systems Landmark™ 2000 Structural System The Landmark™ 2000 Structural System Employs a special truss purlin (an open web roof secondary structural member) that is exclusive to Butler. For more information click here Widespan™ Structural System Providing the practicality of a rigid frame combined with almost unlimited design flexibility to meet your needs. For more information click here Tier I and Tier II Classic Building System Fast, flexible and affordable design options For more information click here