Abstract: This invention relates to a method of making an article from a thermoplastic sandwich material, the normals of at least two surfaces of said material mutually forming an angle, said sandwich material comprising a foam core of a thermoplastic foam and top layers of a thermoplastic synthetic material, which top layers are reinforced with woven fabric, knitted fabric, fibre web or unidirectionally applied fibres, comprising at least the steps of softening a portion of one of said surfaces of said thermoplastic sandwich material over a distance corresponding at least to the length of the folding line of the angle between the two surfaces, by means of a die, the impression of said die being provided at least partly in the top layer, and folding the two surfaces of said thermoplastic material, the surface that has been softened being thereby disposed on the inside of the angle.