"C" IT, SAY IT
'(<a href="http://www.j-archive.com/media/2011-01-26_DJ_15.wmv">Kelly of the Clue Crew uses paper cups & sheets of paper to demonstrate.</a>) There is little support on one horizontal surface; however, with the load distributed  among several vertical surfaces, you get much stronger support when the paper is ridged this way, from the Latin for "wrinkle"'
corrugated