Abstract: A folding sluice box assembly includes a plurality of generally U-sectioned trough segments having their end portions nested in size progression and hinged to each other to form an overlap of the received portion and the receiving portion. A deformation in the bottom surface of a received portion is aligned on full pivotal extension for mating receipt in a conforming bottom surface opening in the receiving portion, thus interlocking of the assembly into its working configuration. When thus extended the edge of a resilient mat positioned on the bottom surface of the receiving segment abuts the edge of the received segment to effect a substantial seal therewith.