Abstract: A safe having a wall comprising spaced steel plates, a sheathing layer between the plates consisting of hard non-metallic grains of e.g., boron carbide, silicon carbide, boron nitride, diamonds, ceramic oxides and hard metallic grains of e.g., cast iron, metal carbides, nitrides, borides, and silicides, said grains being bound together and to said plates by a hard solder mass having a copper or nickel base. The sheathing layer contains 30-70% by volume of said non-metallic grains (having a grain size of 5 to 20 mm) and metallic grains (having a grain size of 1 to 6 mm) and from 70% to 30% of said hard solder. The ratio of said non-metallic to said metallic grains is 2-4 parts to 1 part by volume. A method for making the sheathing layer is also disclosed.