If now we desire to make a break in the plait any two of the cords are cut asunder at the point where they cross each other, leaving four loose ends A, B, C, D. To make a break the loose ends are joined together in pairs. This can be done in two ways only: (1) A can be joined to C and D to B, forming a vertical break; or (2) A can be joined to D and C to B, forming a horizontal break. The decorative effect of the plait is thus entirely altered by running two of the meshes between the cords into one. By continuing the process all the knots most commonly used in Celtic decorative art may be derived from a simple plait. [Illustration: Regular plaitwork, with one vertical break and one horizontal break] [Illustration: Six-cord plait, with horizontal breaks at regular intervals] [450] This occurs on the second panel of the cross at Llanbadarn Fawr. Let us proceed to trace the process of the evolution of knotwork out of plaitwork by actual instances taken from the Welsh crosses. We have, to start with, good examples of plaits of four, six, and ten cords[451] without any breaks at Nevern, Pembrokeshire; and Llantwit Major, and Margam, Glamorganshire. Next, plaits with a single break only are to be seen at Carew, Pembrokeshire, and Llantwit Major, Glamorganshire; then plaits with several breaks, made quite regardless of symmetry or order, at Golden Grove, Carmarthenshire; and, lastly, breaks made at regular intervals, at Neuadd Siarman, Brecknockshire. When the breaks are made symmetrically at regular intervals, and brought sufficiently near together, the plait ceases to be the most prominent feature in the design, and in its place we get a pattern composed entirely of what (for want of a better name) are called knots. On some of the Welsh crosses (as at Carew and Nevern, Pembrokeshire), however, the breaks are made with sufficient regularity and proximity to produce knots, and yet the knots themselves are not symmetrically placed. The result is a class of interlaced-work, intermediate between plaitwork with irregular breaks and knotwork. The same kind of thing is to be seen on the crosses at Coppleston, Devonshire; and St. Neot, Cornwall. [451] Plaits of an uneven number of cords are seldom used, because they produce lopsided patterns. [Illustration: Cross-shaft at Golden Grove, with panels of irregular broken plaitwork Scale ¹/₁₆ linear] [Illustration: Cross-shaft at Llantwit Major (No. 5), Glamorganshire. Eight-cord plait, with cruciform breaks Scale ¹/₁₂ linear] [Illustration: Eight-cord plaits, with cruciform breaks] [Illustration: Eight-cord plaits, with cruciform breaks] [Illustration: Six-cord plait, with cruciform breaks (Occurring at Llanbadarn Fawr)] [Illustration: Ten-cord plait, with cruciform breaks (Occurring at St. Neuadd Siarman)] [Illustration: Knots derived from a three-cord plait]