Abstract: A key construction for use with a rotary disc tumbler lock wherein the key bits consist of a plurality of single planes formed across the transverse axis of the key shank and spaced parallel thereto with each plane capable of aligning its associated tumbler into an open gate position. A key construction for use with a rotary disc tumbler lock wherein longitudinal restricting wards in a plurality of cross-sectional profiles are formable along the key shank and a warded tumbler with a similarly shaped key entry opening, which warded tumbler is used in a lock associated with the warded key thereby providing a plurality of correspondingly shaped warded key entry openings in the lock and key profile configurations which permits locks and keys to be grouped into different series with a key from one group of locks being restricted from entering the locks of another group even though the bitting codes are the same.