A concrete insert for casting in a concrete wall panel, having a housing having an elongate center portion and two opposing longitudinal sides, and two opposing longitudinal flanges. The elongate center portion is bounded by opposing outer longitudinal bend lines, the elongate center portion defining a longitudinally oriented nut access slot. The opposing longitudinal sides depend inwardly from the opposing outer longitudinal bend lines to opposing inner longitudinal bend lines. The opposing longitudinal flanges depend from opposing inner longitudinal bend lines transversely to the opposing longitudinal sides and extend in mutually divergent relation. The housing and the nut box insert comprise a nut box. The nut box insert comprises at least one resilient layer having resilient end walls compressed against the housing by the compression plate for substantially preventing wet cement from entering the nut box. In another approach, end walls substantially prevent wet cement from entering the nut box.