This must depend on Collingwood's account of the stone and on L. E. Hope's photograph of what seems to have been the only decorated face.

A (top): The slab is edged by a grooved moulding and it appears to taper towards the foot of the stem of a cross which is incised on the slab face. It is impossible to say how much of the stem, which might have terminated with a base or even with another head, had already been lost. It reaches the base of the stone and the cross-arms similarly touch the frame. The cross-head is type D10. The inscription, in Anglo-Saxon capitals, was set in an incised frame and was worn and broken. The following can be made out from Hope's photograph:

[–]MV[N.–]

Collingwood himself read MVN[DI] (1911c, 482–3, and pl. facing 482). If one views the slab with the cross-head at the top, the inscription and the two birds which are carved into the surface between the upper and horizontal arms appear upside down, so it must also have been intended to be read from that end (as shown in Ill. 426). The birds are shown as affronted with displayed wings and their beaks are open as though preening. They each appear to have one leg braced against the cross. The one on the right has a plumed tail.

In the interpretation of this piece much depends on whether one feels it is nearly complete or not. Large and small grave-markers or -covers appear in Northumbria from the seventh to eighth century onwards decorated both with incised and relief crosses. In most of the smaller ones the cross form is complete; in some of the larger ones the base of the cross can be seen, as at Hexham 16 and 17 or Jarrow 16 (Cramp 1984, pls. 181; 96, 520) or York, but in others, such as Monkwearmouth 5 or Jarrow 10 (ibid., pls. 110, 604; 94, 505), the base has not survived. At some stage, as yet undetermined, it became customary for the stem of the cross to have a head at both ends, as in Spennithorne, Yorkshire (Collingwood 1927a, fig. 110) or the many recumbent slabs in the East Midlands produced by the Barnack quarry (Fox 1920–2, pls. III–VI). The form of the cross-head here does not conform to the late types, or the disk-heads, but it is the elegant double-curved type, D10, which is associated with high quality ninth-century work, such as Lastingham, Yorkshire (Collingwood 1927a, fig. 133c). If this were originally an example of the double-headed type, then it is one of the earliest examples. Such an arrangement would then make more sense of the 'upside down' layout of the inscription and the birds, since the slab could be viewed from either end. The closest parallel which survives for the decorative layout of this cross is the smaller slab from Wensley, Yorkshire (ibid., fig. 17b), where two birds with affronted heads are upside down to the spectator at the foot of the cross, and two animals and the inscription are the right way up. The inscription at Wensley is set in a frame, as here, and is a single personal name. The Knells inscription could have been a single personal name, and appears to be in Anglo-Saxon capitals with dot serifs. Okasha (1971, 88–9) dates the stone as possibly eighth to ninth century. The little bird figures may also support this date, since they closely resemble the pair of birds in the 'capitals' of the Vespasian Psalter (BL MS. Cotton Vespasian A1, fol. 30v (Alexander 1978, ills. 145–6)), and those at Nunnykirk, Northumberland (Cramp 1984, pl. 207, 1192). Other birds with everted wings are dated by Wilson to that period (Wilson 1964, 12).

Bailey interestingly traces the origin of the two birds on either side of the cross-head to early Christian art, and demonstrates how the motif persisted in Scotland and the Isle of Man into the Viking age. He suggests that one interpretation of the birds is that they represent souls, although angels are also a possible interpretation (Bailey 1974a, I, 41–2).