Joe Dittmar holds remnants of the World Trade Center — a section from one of the core beams of the South Tower, right, and a bolt from a steel beam.

Joe Dittmar holds remnants of the World Trade Center — a section from one of the core beams of the South Tower, right, and a bolt from a steel beam.

Joe Dittmar holds remnants of the World Trade Center — a section from one of the core beams of the South Tower, right, and a bolt from a steel beam.

Joe Dittmar holds remnants of the World Trade Center — a section from one of the core beams of the South Tower, right, and a bolt from a steel bea