If two horizontal breaks and two vertical breaks are made next to each other in a plait, a space in the shape of a cross is produced. A large number of the interlaced patterns used in Celtic decorative art are derived from a plait by making cruciform breaks at regular intervals. There are examples of this in Wales, at Neuadd Siarman, Brecknockshire; Llanbadarn Fawr, Cardiganshire; and Llantwit Major, Glamorganshire. It is not unlikely that symbolism had something to do with the frequent use of the cruciform break. There are eight elementary knots which form the basis of nearly all the interlaced patterns in Celtic decorative art, with the exception of those already described. Two of the elementary knots are derived from a three-cord plait, and the remaining six from a four-cord plait. [Illustration: Knot No. 1] [Illustration: Knot No. 2] =Knot No. 1= is derived from a three-cord plait by making horizontal breaks on one side of the plait only, and =No. 2= by making horizontal breaks alternately on one side and the other. =Knot No. 3= is derived from a four-cord plait by making horizontal breaks in the middle of the plait. =Knot No. 4= is derived from No. 3 by making a horizontal break at A; and =No. 5= from No. 4 by making a vertical break at B and C. =Knot No. 6= is derived from a four-cord plait by making horizontal breaks in the middle of the plait, in the same way as in the case of knot No. 3, but closer together. [Illustration: Knot No. 4] [Illustration: Knot No. 3] [Illustration: Knot No. 5] [Illustration: Knot No. 7] [Illustration: Knot No. 6] [Illustration: Knot No. 8] =Knot No. 7= is derived from No. 6 by making a vertical break at B; and =No. 8= from No. 6 by making vertical breaks at B and C. If a series of knots repeated in a single row can be derived from a plait of _n_ bands, a series of the same knots repeated in a double row can be derived from a plait of _2n_ bands. Thus a pattern composed of knot No. 1 arranged in a double row would be derived from a plait of six cords. Knots like Nos. 3 and 4, which are longer than they are broad, can be placed either horizontally or vertically. Thus No. 3 placed with its longer axis vertical can be derived from a four-cord plait, but if placed horizontally it would be derived from a six-cord plait. [Illustration: Method of deriving Knots Nos. 3 and 6 from a four-cord plait] Knot No. 2 does not occur on the Welsh crosses, and No. 1 only in a double row, as at Neuadd Siarman, Brecknockshire. This pattern is derived from a six-cord plait by making horizontal breaks in the two edges of the plait, and vertical breaks in the middle, the stages being shown on the annexed diagram. Knot No. 3, in a single row placed with its longer axis vertical, occurs at Llandough, Glamorganshire, and, in a single row placed the other way, at Margam, Glamorganshire. [Illustration: Knots Nos. 4, 5, 7, and 8, derived from a four-cord plait]