1.   A stickler, Arthur reportedly could tell by sight if a beam had an eighth-of-an-inch slope.

2.   If the beams have reciprocating saw tracks, they were probably cut sometime in the last century.

3.   The resulting electron beam has exactly the same cross-section shape as the laser pulse that created it.

4.   Those beams have a far lower power output than the giant Omega, but achieve their cutting abilities by concentrating that power steadily over time.

5.   Very old beams may have straight saw marks in an unevenly spaced, zigzag pattern.

6.   One theory on the collapse is that some beams did not have adequate fireproofing, causing them to weaken more quickly.