"Stacking" is the way you stand a dog for a show - so the judge can evaluate them. Front legs straight down from the shoulders, rear legs set with hocks perpendicular to the ground and a paw wider than the front, back flat, head up, neck arched. It's a good way to get a 'picture' of the dog before you do the hands-on exam, and lets you see the various important angles and proportions.
