Method for manufacturing a first elongated tube of a telescopic column for a height-adjustable furniture, wherein the first elongated tube is to have a length (l 1) along a longitudinal center axis (X-X), to have a circular cross-section perpendicular to the center axis with a circumference (c), to co-operate with a second elongated tube of a smaller circular cross-section than the first elongated tube, and to have a first elongate protrusion arranged on an inner side of the first elongated tube, the protrusion extending along the center axis (X-X) for co-operation with one or more second protrusions arranged on an outer side of the second elongated tube so as to prevent rotation between the first elongated tube and the second elongated tube when the first elongated tube and the second elongated tube are mounted together in a telescopic column, the method comprising: obtaining a square-shaped flat material sheet having a length (l 0) along a longitudinal axis (X 0 -X 0) corresponding to the length (l 1) of the manufactured first elongated tube, and a width (w 0) perpendicular to the longitudinal axis (X 0 -X 0) from a first edge to an opposite second edge that is greater than the circumference (c) of the manufactured first elongated tube, folding the flat material sheet, at a longitudinal demarcation line (d; d 1, d 2) arranged between a first part (116; 119) having a length corresponding to the length (l 0) of the flat material sheet and a width (w 01) corresponding to the circumference (c) of the manufactured first elongated tube, and an end part (117, 118; 120) having a length corresponding to the length of the flat material sheet and a width (w 02) corresponding to a width of the first elongate protrusion of the manufactured first elongated tube, so that the end part (117, 118; 120) is folded towards a first side of the flat material sheet that is to become the inner side of the first elongated tube, such that a fold is created, bending the first part (116; 119) of the flat material sheet along the longitudinal axis (X 0 -X 0) into a tube-shaped form such that the first side becomes the inner side of the first elongated tube, and such that the end part (117, 118; 120) forms the first elongate protrusion, and bonding a joint at the fold of the tube-shaped form together such that the cross-section of the first elongated tube is seamless, wherein the flat material sheet is folded at the demarcation line (d; d 1, d 2) such that a first side of the end part (117, 118; 120) bears against a first side of the first part (116; 119), wherein the end part comprises two end parts (117, 118) mutually separated by the first part, and the demarcation line (d) comprises a first demarcation line (d 1) arranged between a first of the two end parts and the first part, and a second demarcation line (d 2) arranged between a second of the two end parts and the first part, and wherein the folding comprises folding the flat material sheet at the first demarcation line (d 1) creating a first fold and folding the flat material sheet at the second demarcation line (d 2) creating a second fold, and wherein the bending is performed such that the first fold and the second fold meet at their demarcation lines (d 1, d 2), and wherein the bonding of a joint is performed where the first and the second fold meet, and wherein the first and the second end parts (117, 118) are folded so that they bear against the first part. obtaining a square-shaped flat material sheet having a length (l 0) along a longitudinal axis (X 0 -X 0) corresponding to the length (l 1) of the manufactured first elongated tube, and a width (w 0) perpendicular to the longitudinal axis (X 0 -X 0) from a first edge to an opposite second edge that is greater than the circumference (c) of the manufactured first elongated tube, folding the flat material sheet, at a longitudinal demarcation line (d; d 1, d 2) arranged between a first part (116; 119) having a length corresponding to the length (l 0) of the flat material sheet and a width (w 01) corresponding to the circumference (c) of the manufactured first elongated tube, and an end part (117, 118; 120) having a length corresponding to the length of the flat material sheet and a width (w 02) corresponding to a width of the first elongate protrusion of the manufactured first elongated tube, so that the end part (117, 118; 120) is folded towards a first side of the flat material sheet that is to become the inner side of the first elongated tube, such that a fold is created, bending the first part (116; 119) of the flat material sheet along the longitudinal axis (X 0 -X 0) into a tube-shaped form such that the first side becomes the inner side of the first elongated tube, and such that the end part (117, 118; 120) forms the first elongate protrusion, and bonding a joint at the fold of the tube-shaped form together such that the cross-section of the first elongated tube is seamless,