Warp knitting is a type of knitting methods in which the yarn zigzags along the length of the fabric, i.e., following adjacent columns ("wales") of knitting, rather than a single row ("course"). For comparison, knitting across the width of the fabric is called weft knitting.
When producing warp-knits, a yarn sheets is linked by stitches in longitudinal direction. Thus, each individual thread in the sheet (warp) forms a wale.
In a warp knitted structure each loop in the horizontal direction is made from different thread. At least one yarn is required for each needle.
As a result yarns are fixed in a structure and loops are not pulled out easily.