of less than or equal to the diameter of the machine direction md or cross machine direction cd yarns at the ends 212 214 this diameter can be of the yarn as new as used or after a compaction or pressing step as heretofore mentioned the pattern of the stitching used may take on various forms such as zig zag chain or lock stitch patterns the depth of the stitch in the fabric may also vary also it may be desired to have a preliminary stitch to generally affix or align the spiral 220 on ends 212 214 and once aligned implement a main stitching also once the stitching is completed one or more rows of additional stitching parallel to ends 212 214 or in the cross machine direction cd and across the attachment stitching attaching the spiral might be used to reinforce the spiral attachment as much stitching that is required should be within the plane of the fabric thickness there are multiple variations of what may be done as aforesaid once the stitching is completed the ends 212 214 may be treated to otherwise stabilize the ends 212 214 and reinforce and smooth the stitching thereon note the size dimension or material in the spirals does not have to be the same in top and bottom the bottom can be load bearing and the top designed to even out the pressure distribution and or permeability different material top bottom may also be desired the spirals do not have to be combined with the same loop density as the fabric layer or have the same density in the top and bottom for a coarse bottom spiral it would be useful to connect that with gt 1 loop.