A body portion has opposed ends spaced centrally by a length. The body portion has opposed concave sides. The concave sides are spaced by a minimum width when measured at the midpoint of the length. The body portion has planar upper and lower surfaces. A vertically oriented projection extends upwardly from the upper surface of the body portion. The body portion has a lower edge centrally positioned on the longitudinal axis of the body portion. The projection has an upper edge centrally positioned above the longitudinal axis of the body portion. The projection has a forward end in a generally triangular configuration. The projection has a rearward end in a generally triangular configuration. The forward end has a thickness greater than the thickness of the rearward end.