This is probably a complete or near-complete rectangular grave-marker, of which two thirds is buried in the wall in which it has been reset. Both faces have incised decoration.

A (broad, presently facing upwards): Decorated with a narrow border defined by a single line and, within, a panel of incised geometrical ornament. The pattern is formed by a grid of lines at right-angles to the borders of the stone, which is overlaid with a second grid of lines running diagonally. The intersections of the diagonal grid coincide with crossings in the rectangular grid.

C (broad, presently facing downward): This has lost its original border as the edge has been given a neat chamfer, probably when it was reset in its present position. Within, there is a diagonal grid superimposed on an incised rectangular cross (type A1). The result is that the diagonals fill the upper two interstices above the cross-arms.

The decoration on face C is valuable as it hints at the underlying intention behind the decoration on face A and on related stones. The decoration seems conceived as a simple cross (type A1) with diagonal lines decorating the interstices, although on face A the basic cross form is reduced to a single line. The Swarby grave-marker clearly belongs to the same group of 'gridded' markers as Ancaster 1 (Ill. 10) and Wilsford 2 (Ill. 391), which share the same stone type and decorative repertoire (Chapter V, Table 7C). At Wilsford, not only is the same decoration used (though on one face only) but the marker was reused for the same purpose in the later Middle Ages. The fragmentary markers at Bicker (no. 4, Ills. 49–52) and Gosberton (no. 1, Ill. 175), as well as the nearly identical marker at Barnack itself, are clearly related stylistically to this group but are made of the different, Barnack stone.

The Swarby marker, along with those at Wilsford and Ancaster, may date from the end of the tenth century, but is perhaps more likely to belong to the early eleventh.