are sealed and there are no stray ends of filaments fig1 shows diagrammatically an assembly of track modules arranged for forming an i structure braid the assembly being similar to that shown in fig1 the gear modules that are under the track modules are also shown diagrammatically in fig1 the array of slotted gear wheels or horngears 1 2 11 and 12 shown in fig1 comprise 16 rows of horngears the middle 8 rows being shorter in that they have less columns than the other rows and being disposed symmetrically relative to them there is a common drive arrangement 20 including a prime mover 21 and a drive gear 22 which meshes with one 2 of the horngears 1 and 2 of one of the outer longer rows of the array the longer rows of the array comprise a row of 20 horngears 1 and 2 or 11 and 12 each having four slots 3 which are arranged in a cruciform pattern and a turnaround horngear 9 10 at either end the arrangement is substantially as is described with reference to fig9 so that the turnaround horngear 10 at one end of each of the outer longer rows has 5 equiangularly spaced slots 3 and is adjacent.