On Chowhound, dennis7490 wants to know why his roasting pan has a "moat," an indentation that runs all the way around the perimeter. He thinks a totally flat pan would be ideal, since this shallow ditch makes it really hard to make pan gravy. Does it serve some purpose dennis7490 doesn't know about?
One theory: It's a clueless cookware designer's idea of a built-in roasting rack, jjjrfoodie says. In theory, the "moat" drains away the juices from the meat as it cooks, keeping the steam at bay to help it dry-roast.
Of course, a rack set in a flat pan would work much better—an effective built-in roasting rack would have to be much higher than the raised surface in, say, dennis7490's pan. Besides, sandylc says, a narrow indentation wouldn't be very good at keeping moisture away from the roast anyway.
Alan408 has another theory: The moat helps keep a relatively thin roasting pan from warping in the oven. Note that flat roasting pans tend to be thicker and heavier (and usually more expensive). That running indentation? Nothing more than engineering, to give the pan stability when things heat up.
Discuss: Roasting pan moat
Photo from Sur La Table