Abstract: A device knits together a tubular structure of continuous fibers with a stitch yarn, to provide a reinforcing substrate, especially for use with roofing materials. The device brings together first and second sets of the continuous fibers at a cylinder with a plurality of latch needles. The first set of fibers enter the cylinder radially in interstitial spaces between adjacent needles. At least one continuous fiber constituting the second set of fibers enters the cylinder tangentially at an insertion point. Axial manipulation of the needles at the insertion point results in knitting the stitch yarn around the intersecting first and second continuous fibers, resulting in the knitted tubular structure. The manipulation is achieved by rotating the means by which the second fibers and the stitch yarn are introduced, as well as the means for manipulating the needles, in a stepwise sequential manner around the circumference of the cylinder.