A structural technique in which alternate warp threads are pulled to a second, lower level inside the rug, so the knots pack into two planes instead of one. This is the hidden engineering behind many very finely knotted carpets: it nearly doubles the achievable knot density and produces a stiff, heavy handle. Running your fingers across the back of a rug and feeling ribbed, offset knot nodes is a classic connoisseur's test for warp depression.