The invention relates to a lock assembly (10) of a planar component (22) displaceably mounted in frame (30). Said assembly (10) comprises an engaging element (40) which, in said planar component's closed position, can be fixed in place in a latching system (50). Said latching system is designed in a manner that, in its blocked position, the engaging element, for instance a bar affixable by compression and/or friction in the latching system (50), can be inserted into latter in a first direction (R) opposite the direction of closing (X) of the planar component (20), whereas such insertion is blocked in a second direction (S) which is opposite said planar component's direction of opening (O). This design allows almost noiselessly operating the lock assembly. The planar component also may be closed when the latching system is in the blocked position already when the planar component is open. Moreover all double fittings are averted and as a result the said planar component always can be closed and be locked in play-free manner.