The chairs are back in Yarmouth, cloaking the sides of Main Street in bright vinyl, white plastic and checkered webbing.

Straddling a fine line between inside joke and genuine desire for a premium view, the annual chair migration for the 50th Yarmouth Clam Festival is on schedule, with those of the ambitious sort setting up weeks prior to the July 17 parade.

“When we did this years ago, you’d set up a couple of days before. Now, you need to do it at least a week ahead,” said Nikki Evans, a Falmouth resident who comes to the festival every year, and was setting up her chairs Friday.

Most are secured in place with bright rope or cord, attached to street signs or other immovable objects, serving as the lawn chair equivalent to a bike lock.

“This is a local cultural phenomenon, and I view it through a lens of interesting psychological behavior,” said Sarah Victor, a massage therapist who works in Yarmouth. “I’ve observed everyone setting up weeks in advance, and a lot of my clients set up their chairs in front of their own Main Street houses, because if they don’t, someone else will get their spot, Victor said