Cutting across a ceiling in MASS MoCA, a rusty wall divides 120 feet of the museum’s length. The artist who built the wall—ERRE—has recreated the barrier at the San Ysidro Port of Entry, the main checkpoint between Tijuana and San Diego. Only here the wall announces a deepening of space rather than a divide. A survey of ERRE’s work, gathered within the space, addresses the powerful bond between the U.S. and Mexico, and conflicts both real and imagined. —C.J.F.