 The top of each line is attached to small fabric loops sewn into the structure of the wing, which are generally arranged in rows running span-wise (i.e., side to side).The row of lines nearest the front are known as the A lines, the next row back the B lines, and so on.A typical wing will have A, B, C and D lines, but recently, there has been a tendency to reduce the rows of lines to three, or even two (and experimentally to one), to reduce drag.