A label with top, bottom and edge surfaces is attached to a thermoplastic substrate by a method comprising the steps of:A. Placing the bottom surface of the label in contact with a surface of the substrate;B. Melting a portion of the substrate beneath the label or adjacent to an edge of the label;C. Drawing a portion of the melted substrate over an edge of and onto the top surface of the label such that the portion of the melted substrate on the top surface of the label is continuous with the substrate; andD. Solidifying the melted substrate.The attachment does not require adhesive or mechanical fasteners, and the label and thermoplastic substrate can be made of any material that will withstand the conditions of the environment to which they will be exposed.