Abstract: Housing (1, 20) for lodging conventional flat keys or keys of a special kind (2, 2a, 2b'-2b", 2c, 2d), in a safe but removable way. The laminar housing (1, 20) is realized by elastically flexible plastic material s of a type and form like a rectangular "credit card", and it is provided with a central opening (5, 21) whose peripheral edge (10, 22) defines a space for lodging a key or more superimposed keys. At the site of the opening (5, 21), elastic seizing elements (7--7) may project out of the housing (1, 20) acting on the lateral fins of the heads (3, 3a, 3b, 3c) or on the stems (4, 4a, 4c, 4d) of the keys.