A basket for receiving heat transfer elements for a rotary air preheater, the basket comprising: two metallic frames (20, 20') each having two elongate corner pieces (22A, 22B, 22A', 22B') and two elongate connector pieces (24A, 24B, 24A', 24B'), each of the corner pieces (22A, 22B, 22A', 22B') having a two leg angled cross section, for each frame (20, 20') one of the connector pieces (24A, 24B, 24A', 24B') is secured to one end of each of the corner pieces (22A, 22B, 22A', 22B') and another of the connector pieces (24A, 24B, 24A', 24B') is secured to an opposite end of each of the corner pieces (22A, 22B, 22A', 22B') such that the corner pieces (22A, 22B, 22A', 22B') are spaced apart from and parallel to one another and the connector pieces (24A, 24B, 24A', 24B') are spaced apart from and parallel to one another thereby forming a rectangular opening (29, 29') in each frame (20, 20'); whereby metallic sheets (30, 30') are connected to the corner pieces (22A, 33B, 22A', 22B'), thereby forming a channel, the channel having a longitudinal axis that is parallel to and bounded by the corner pieces (22A, 33B, 22A', 22B'), the channel being configured to receive heat transfer elements having a flow direction coaxial with the channel; and the sheets (30, 30') being a barrier for preventing lateral bypass of gas and air flow between sides of the baskets at edges of the heat transfer elements disposed in the baskets; characterized in that the metallic sheets (30, 30') are two heavy gauge metallic sheets (30, 30') configured to withstand wear and cracking from soot blowing, each sheet (30, 30') having opposite edges (30A, 30B. 30A', 30B') secured longitudinally along an outside surface of one of the corner pieces (22A, 22B, 22A', 22B'), thereby structurally supporting and spacing the frames (20, 20') equally apart from and parallel to one another thereby forming a channel between two of the sheets (30, 30'). two metallic frames (20, 20') each having two elongate corner pieces (22A, 22B, 22A', 22B') and two elongate connector pieces (24A, 24B, 24A', 24B'), each of the corner pieces (22A, 22B, 22A', 22B') having a two leg angled cross section, for each frame (20, 20') one of the connector pieces (24A, 24B, 24A', 24B') is secured to one end of each of the corner pieces (22A, 22B, 22A', 22B') and another of the connector pieces (24A, 24B, 24A', 24B') is secured to an opposite end of each of the corner pieces (22A, 22B, 22A', 22B') such that the corner pieces (22A, 22B, 22A', 22B') are spaced apart from and parallel to one another and the connector pieces (24A, 24B, 24A', 24B') are spaced apart from and parallel to one another thereby forming a rectangular opening (29, 29') in each frame (20, 20'); whereby metallic sheets (30, 30') are connected to the corner pieces (22A, 33B, 22A', 22B'), thereby forming a channel, the channel having a longitudinal axis that is parallel to and bounded by the corner pieces (22A, 33B, 22A', 22B'), the channel being configured to receive heat transfer elements having a flow direction coaxial with the channel; and the sheets (30, 30') being a barrier for preventing lateral bypass of gas and air flow between sides of the baskets at edges of the heat transfer elements disposed in the baskets; characterized in that the metallic sheets (30, 30') are two heavy gauge metallic sheets (30, 30') configured to withstand wear and cracking from soot blowing, each sheet (30, 30') having opposite edges (30A, 30B. 30A', 30B') secured longitudinally along an outside surface of one of the corner pieces (22A, 22B, 22A', 22B'), thereby structurally supporting and spacing the frames (20, 20') equally apart from and parallel to one another thereby forming a channel between two of the sheets (30, 30').