An extendible truss boom (18) is attachable to a materials handling vehicle (10). The truss boom includes a connector frame (20) coupleable with the materials handling vehicle. A plurality of truss frame members (22) are affixed at one end to the connector frame and at an opposite end to an end bracket (24), which defines an extension opening (28). An extension member (30) is movably supported by the end bracket in the extension opening. The extension member is selectively lockable in the extension opening in a plurality of positions between a fully retracted position and a fully extended position.