<font face="Verdana, Arial, Helvetica, sans-serif" size="2">Originally posted by WHBM:
Called a "cheat" line because a horizontal line "cheats" or "tricks" the eye into thinking the object it is applied to is longer/sleeker than it actually is - which is why airlines use it in their colour schemes, of course.</font>
I just picture the sales pitch to the airlines from the painters:
"Add inches painlessly without surgery or suction devices!! Your passengers will beg for more! "
