Abstract: A wall panel consisting of two laminar units each including a core layer of particulate, sintered, aluminum oxide, a perforated metal shell enveloping the layer, and a continuous mass consisting essentially of elastomeric material enveloping the shell and extending into the layer through the perforations of the shell. The mass bonds the particles in the layer to each other and to the shell, and the two masses constitute a unitary body connecting the shells in a position in which the core layer of one unit projects beyond the core layer of the other unit so as to define a rabbet. Two such panels may engage each other in a rabbet joint in which the projecting core layer parts are spacedly superimposed on each other to provide a burglar resistant connection between the panels which themselves are difficult to penetrate by burglar's tools.