Boxed

What does the highlighted "boxed" mean?

Context:

What was generated around the formation of britart.com was a rhetoric not only of the affordability but also of the now more relational or personalised approaches that characterise contemporary art, reflected in the direct-mail strand of the campaign. The mailings invited the interactivity of the recipients and, in some cases, gave them a producerly role to play: for example, the boxed‘Art Pencil’ that held the promise that everything it drew would
become art. That an avant-garde gambit such as this is now used as a means of advertising art rather than as means of disrupting convention through art shows that conceptualism has become a form of popular, if not exactly common, currency.