Geometrically, an open loop is one in which the forming yarns do not cross at the bottom of the loop. In a closed loop, yarn crossing takes place.

• 按几何形状分类时,如果形成线圈的纱线不在线圈的底部交叉,则称为开口线圈;如果在底部发生纱线的交叉,则称为闭口线圈。