A method for the design of an addendum, wherein all or part of the addendum is designed in a sectionless approach, comprising the steps of: inputting a component design; establishing a plurality of at least two elevation curve, EC, lines to establish at least a first EC line and a distal EC line, wherein said first EC line is related to, or fully or partially established on said component design, and said distal EC line is fully or partially separated from said first EC line so as to establish a space between said first and said distal EC lines (120, 122); and filling the space between said first and distal EC lines (120, 122) so as define said addendum; characterized in that the design of said addendum is controlled by establishing continuity conditions at any or all EC lines, and interconnection of the spaces between any or all EC lines is accomplished using a surface based or mesh based parameterized filling technique, and wherein: i) said distal EC line, or any additional EC lines, is established from another EC line using incremental part extension, IPE, comprising: representing an EC line in a tessellated form as a 3D polyline; at each boundary point on the polyline, establishing a normal vector and tangent vector; projecting an extension from each point on the current boundary, using said normal and tangent vectors, so as to create a collection of new extension points; connecting said new extension points so as to create a new 3D polyline, separated from the previous 3D polyline extension, on the extension points; and repeating the above steps of extending a layer until a desired total size for the extension is achieved, and said projected extensions produce a distal EC line from a first EC line on said component; or ii) said addendum is determined by a process which comprises determination of the DieFace Side Surface, DFSS, from an EC line comprising: a) projecting a projection of an EC, offsetting said projection to prepare a first approximation of a further EC line, and filling said surface with a draft surface between said EC line and said first approximation of said further EC line; or b) projecting a draft surface at an angle that starts from said EC line, and thus produces a first approximation of a further EC line. i) said distal EC line, or any additional EC lines, is established from another EC line using incremental part extension, IPE, comprising: representing an EC line in a tessellated form as a 3D polyline; at each boundary point on the polyline, establishing a normal vector and tangent vector; projecting an extension from each point on the current boundary, using said normal and tangent vectors, so as to create a collection of new extension points; connecting said new extension points so as to create a new 3D polyline, separated from the previous 3D polyline extension, on the extension points; and repeating the above steps of extending a layer until a desired total size for the extension is achieved, and said projected extensions produce a distal EC line from a first EC line on said component; or representing an EC line in a tessellated form as a 3D polyline; at each boundary point on the polyline, establishing a normal vector and tangent vector; projecting an extension from each point on the current boundary, using said normal and tangent vectors, so as to create a collection of new extension points; connecting said new extension points so as to create a new 3D polyline, separated from the previous 3D polyline extension, on the extension points; and repeating the above steps of extending a layer until a desired total size for the extension is achieved, and said projected extensions produce a distal EC line from a first EC line on said component; or ii) said addendum is determined by a process which comprises determination of the DieFace Side Surface, DFSS, from an EC line comprising: a) projecting a projection of an EC, offsetting said projection to prepare a first approximation of a further EC line, and filling said surface with a draft surface between said EC line and said first approximation of said further EC line; or b) projecting a draft surface at an angle that starts from said EC line, and thus produces a first approximation of a further EC line. a) projecting a projection of an EC, offsetting said projection to prepare a first approximation of a further EC line, and filling said surface with a draft surface between said EC line and said first approximation of said further EC line; or b) projecting a draft surface at an angle that starts from said EC line, and thus produces a first approximation of a further EC line.