A method of manufacturing a metal part (10, 36, 410), said part extending in a first direction and having a cross-section comprising a central element and at least a first side element extending in a second direction, the first and second directions being different from each other; the method comprising the following steps: - providing a metal blank of substantially rectangular cross-section, said blank extending in the first direction; - at least one step of removing material from the metal blank, so as to form an intermediate part comprising the central element, extending in the first direction; a joining zone and at least first and second intermediate lateral elements, extending in parallel substantially in the first direction from said joining zone, opposite the intermediate central element; a space being provided between the first and second intermediate lateral elements; - at least a first hot deformation of the intermediate part, said first deformation comprising heating of the intermediate part, the process being characterised in that it further comprises the following steps: - A step of clamping the central element between two movable elements (202, 204) of a die, perpendicularly to the first direction, the joining zone and the first and second intermediate lateral members (116, 118) then being arranged above the said members (202, 204) of the die; then - a step of separating the first and second intermediate lateral members (116, 118) by inserting a first punch between said first and second members, the central member being clamped in the die during insertion of the first punch. the method comprising the following steps: - providing a metal blank of substantially rectangular cross-section, said blank extending in the first direction; - at least one step of removing material from the metal blank, so as to form an intermediate part comprising the central element, extending in the first direction; a joining zone and at least first and second intermediate lateral elements, extending in parallel substantially in the first direction from said joining zone, opposite the intermediate central element; a space being provided between the first and second intermediate lateral elements; - at least a first hot deformation of the intermediate part, said first deformation comprising heating of the intermediate part, - providing a metal blank of substantially rectangular cross-section, said blank extending in the first direction; - at least one step of removing material from the metal blank, so as to form an intermediate part comprising the central element, extending in the first direction; a joining zone and at least first and second intermediate lateral elements, extending in parallel substantially in the first direction from said joining zone, opposite the intermediate central element; a space being provided between the first and second intermediate lateral elements; - at least a first hot deformation of the intermediate part, said first deformation comprising heating of the intermediate part, the process being characterised in that it further comprises the following steps: - A step of clamping the central element between two movable elements (202, 204) of a die, perpendicularly to the first direction, the joining zone and the first and second intermediate lateral members (116, 118) then being arranged above the said members (202, 204) of the die; then - a step of separating the first and second intermediate lateral members (116, 118) by inserting a first punch between said first and second members, the central member being clamped in the die during insertion of the first punch. - A step of clamping the central element between two movable elements (202, 204) of a die, perpendicularly to the first direction, the joining zone and the first and second intermediate lateral members (116, 118) then being arranged above the said members (202, 204) of the die; then - a step of separating the first and second intermediate lateral members (116, 118) by inserting a first punch between said first and second members, the central member being clamped in the die during insertion of the first punch.