This technique is characterised by the tying thread not appearing on the surface of the ground material. Instead it takes the form of long threads on the back of the ground material. Because the tying thread secures the laid thread on the reverse, it is protected from surface wear, which means this type of embroidery does not wear out as quickly as normal (surface) couching. In addition, the loops of laid thread on the back of the ground material act like a series of small hinges, giving the embroidery a pliability that does not normally occur with surface couching.
Underside couching was widely used in English embrodiery; examples are extant that date from the eleventh to the early fifteenth centuries. It was one of two stitches frequently used for opus anglicanum; the other stitch was split stitch. In English embroidery, the couching thread was normally made of linen.
GVE