an adjustable corner strip for joining adjacent concrete form panels into a column mold includes spaced diverging wings with slots to retain adjustment screws for adjusting the divergence of the wings , and thus the panels . the corner strip permits easy and rigid squaring of forms . a chamfer strip includes a chamfer face and an integrally formed tail section extending outwardly of the strip and adapted to fit into the channel formed along the mold side rail . the adjustable corner strips bring the chamfer strips into tight mating engagement with the interior surfaces of the mold panels , preventing leakage of cement between the chamfer strips and the mold panels .