Abstract: A fabricated window, preferably, though not necessarily, made from extruded shapes and which is so put together as to be suitable for use particularly in those instances where a tamper-proof window is required, by way of example, for use as windows in mental institutions. Particularly, the improved construction comprises means simply to slip the various parts of the window together by the provision of certain groove formations in the jambs, rails, and mullions together with a final assembly part in the corners of the window so secured to certain portions of the window parts as to prevent unauthorized disassembly of the window when the same is in use.