A covering element of a hinge adjusting notch in an edge of an element of a frame assembly defined by a longitudinal projection with a curved cross-section, preferably L-shaped or C-shaped cross-section, characterized in that, it comprises: a main part with an L-shaped cross section comprising a central arm and a side arm, wherein the main part at both ends transforms into bent parts with L-shaped cross sections comprising central arms and side arms, wherein the side arms (22, 32) of the main part and the bent parts are on the same plane, and the central arms of the bent parts extend from the central arm of the main part in the direction of the longitudinal axis of the central arm of the main part and are bent with respect to the plane of the central arm of the main part in the opposite direction relative to the direction of a projection of the side arm of the main part, and wherein the bent parts comprise first positioning projections protruding from their central arms at transverse displacement distances from their side arms and at depth displacement distances from the ends of the central arms of the bent part in the direction perpendicular relative to the plane of the central arm of the main part, wherein the first positioning projections define transverse positioning edges, preferably forming positioning planes, on the side of the side arms of the bent parts and recessed positioning edges, preferably forming positioning planes, on the side of the ends of the central arms of the bent parts, and the main part comprises at least one second positioning projection protruding from its central arm at a second transverse distance from its side arm, preferably equal to the transverse distance of the first positioning projections, wherein the second positioning projection defines a transverse positioning edge, preferably a positioning plane, on the side of the central arm of the main part. a main part with an L-shaped cross section comprising a central arm and a side arm, wherein the main part at both ends transforms into bent parts with L-shaped cross sections comprising central arms and side arms, wherein the side arms (22, 32) of the main part and the bent parts are on the same plane, and the central arms of the bent parts extend from the central arm of the main part in the direction of the longitudinal axis of the central arm of the main part and are bent with respect to the plane of the central arm of the main part in the opposite direction relative to the direction of a projection of the side arm of the main part, and wherein the bent parts comprise first positioning projections protruding from their central arms at transverse displacement distances from their side arms and at depth displacement distances from the ends of the central arms of the bent part in the direction perpendicular relative to the plane of the central arm of the main part, wherein the first positioning projections define transverse positioning edges, preferably forming positioning planes, on the side of the side arms of the bent parts and recessed positioning edges, preferably forming positioning planes, on the side of the ends of the central arms of the bent parts, and the main part comprises at least one second positioning projection protruding from its central arm at a second transverse distance from its side arm, preferably equal to the transverse distance of the first positioning projections, wherein the second positioning projection defines a transverse positioning edge, preferably a positioning plane, on the side of the central arm of the main part.