Panels for assembling a sandbox frame include an elongate A panel and an elongate B panel. Each panel has an end portion terminating in an end edge. The end edge is oriented transverse to the length dimension of the panel. A first cord receiving notch is disposed in the A panel end edge. A second cord receiving notch is disposed in the B panel end edge. A first elongate A slot is proximate the A panel end portion. The first slot is oriented transverse to the length dimension of the A panel. A second elongate B slot is proximate the B panel end portion. The second slot is oriented transverse to the length dimension of the B panel. A first groove is disposed in the A panel end portion. The first groove is oriented transverse to the A panel length dimension. The groove is recessed from a main surface of the A panel and defined by opposed groove walls wherein one of the groove walls is beveled. When the A and B panels are assembled, the A panel slot interlocks with the B panel slot. The A panel slot captures a B panel wall portion adjacent the B panel slot. The B panel slot captures an A panel wall portion adjacent the A panel slot. The A panel end portion and the B panel end portion intersect.