Abstract: A retaining rod is provided for forcing a tight interfit between adjacent segments of a liner of a casting shake-out unit, sand reclaimer, rotary media drum, or a tumbling unit. The adjacent edges of the liner segments have triangular grooves which combine to create diamond shaped channels between adjacent segments of the liner. The rod is generally diamond shaped in cross-section and tapered from front to back, giving the rod an overall trapezoidal appearance. The cross-sectional height of the rod is greater than the cross-sectional width of the rod. Thus, the rod can be placed in the channel in one of two positions and the same rod may be used if the clearance between adjacent segments is large or small simply by rotating the rod 90.degree..