C. Pat Structure System.

Here the pats, numbers are taken down from the ``upper'' side of the pat to the ``lower'' side in both cases; in flexing, the ``lower'' side is folded together. Again, both steps are shown in flexing.

$$\begin{array}{lllllllllll} \;\; & P_h\{k_0\} \; ; \; P_i\{n_m... ..._0\} &; & P_h^*\{k_0\}& & &\qquad &\qquad & (T)\\ \end{array}$$

$$\left. \begin{array}{lllllllll} \;\; & (1) & P_h\{k_0\} & , &... ...\{k_0\} & ; & P_i^*\{n_0\} & \end{array}\right\} \; {\em (F)}$$

In each of the above cases, the leaves were numbered in a specific direction along the plan. This direction is that in which the pats are arranged in the sequences of leaves shown. If the direction is changed, the signs associated with terms in part $A$ must be changed and changes must be made in the subscripts of part $C$. Since changing the direction of labeling the strip is equivalent to changing which pat is broken up in flexing, we will give the flexing operation for a ``left-handed'' flex, which will then suffice for both of these contingencies: A left-handed flex = right-handed flex in a plan numbered backwards.