Abstract: A device for comminuting material comprising first and second mating sections. The mating sections when mated form an enclosed interior chamber with the first and second sections capable of movement relative to each other. The first mating section has a first set of a plurality of pins, which extend from a base of the first mating section and into the interior of the chamber. Similarly, the second mating section has a second set of a plurality of pins extending from a base of the second mating section and into the interior of the chamber. The pins from the first mating section interdigitate with the second set of a plurality of pins when the first and second mating sections are mated, wherein movement of the first and second mating sections relative to one another causes comminution of the material when placed in the chamber. The pins have varying cross-sectional shapes including circular, triangular, and hexagonal.

Abstract: A method and means are provided for stopping erosion of beach areas and restoring the same by wave and wind activated formation of new dunes, by erecting on the beach area an elongate frame and screen structure of lightweight materials and anchoring said structure to the ground. The frame members are arranged and interconnected to form a plurality of tetrahedral units which, in turn, are assembled so as to present to incoming waves a zigzag-shaped wall composed of screen sections inclined upwards and landwards, whereby to subject the structure to forces tending to press it down towards the ground and thus to retain it in position even before it is buried in accumulating sand masses. The invention includes special means for interconnecting the frame members and for anchoring the structure.