Abstract: A flat key for a tumbler-containing locking cylinder of a locking apparatus, with a key grip and, attached thereto, a key shank for locking grooves cut into the shank towards the end surface, the shank having a basic profile exhibiting an essentially T-shaped cross-sectional configuration, of which the T-bar forms a guide bar with guiding surfaces, and of which the T-stem extending in the longitudinal mid-plane provides the end surface and has wide side surfaces for the provision of profile ribs that have curvilinear cross-sectional contours.

Abstract: A locking cylinder (1) with a cylindrical housing (2) of which the core bore (7) receives a cylindrical core (8) having a key channel (9) with core pins provided in the cylindrical core and housing pins displaceably guided in housing pin bores, the housing pins being resiliently biased by springs in the direction of the core pins, and with at least one additional, core-adjacent tumbler element (15) adjacent the wide-side profile of the key, the element (15) being displaceable in a cavity (H) crossing the rotational interface of the cylindrical core, the tumbler element being spring biased in the outward direction of the core and having a control projection (22, 51) projecting sidewards into the key channel (9, 43).

Abstract: A cylinder lock has a housing with a rotatably insertable cylinder having a key passage for an insertable flat key whose front part has locking notches associated with cylinder pins arranged in openings of the cylinder for retaining the cylinder pins. The flat key is provided at both its lateral sides with longitudinal grooves for receiving longitudinal ribs provided on the lateral sides of the key passage for the lateral profile variation. The longitudinal grooves on both lateral faces of the flat key lie with their bottom faces on lines which extend parallel to and at a distance from one another. The parallel lines extending at a distance from one another are arcuate at least in one partial region, and the convexly protruding central part of one arcuate line extend at least close to a straight line connecting the end points of the second arcuate line.