http://www.pmq.com/mag/2004may_june/packaging.php

PCE is another Hot Feature of the Future. PCE stands for Pizza Carton Elevation. It results from placing legs on a corrugated pizza carton (previously referred to as Hot-legs in a past issue of PMQ). Virtually any style of carton can be equipped ... including your current pizza box. Here's how PCE works. In a customer's home, a pizza in a non-legs carton experiences 33 percent greater heat loss than a pizza in a legs-equipped carton. Also, without legs, the box bottom absorbs condensation that forms on a tabletop, whereas with a legs-equipped box a tabletop stays dry. Finally, a package with a soggy, water-soaked bottom panel projects a low-quality image.