the.com/milk carton

means A paperboard container for milk that became famous for printing photos and descriptions of missing children on its sides.

from The waxed paperboard milk carton was developed in the early 1900s as a cheaper, disposable alternative to glass bottles. The 'missing child' association comes much later: in the early 1980s, dairies and nonprofits in the US began printing photos of missing children on cartons, after a few high-profile child disappearances made national news. The practice spread quickly, became a cultural fixture through the decade, and then faded as other media — flyers, TV alerts, and eventually the internet — took over that role.