Drops of 12 in (30.5 cm) or more in a line of sluices that are formed by allowing the discharge end of one box to rest on the head of the succeeding sluice, instead of telescoping into it. This method ensures a drop of 12 in or more (depending on the depth of the sluice box) at the end of each sluice, which usually is sufficient to disintegrate fairly stiff clay.