Method of securing knobs

A method of securing to an operating lever in the form of an elongated metal plate an operating button made of thermoplastic resin and including a mounting tongue of a generally tubular configuration having a hollow defined therein. An anchor perforation and a stopper pawl are first formed in the operating lever and the operating button is then temporarily mounted on the operating lever with the operating lever slid into the hollow of the mounting tongue until an abutment defined in the mounting tongue and positioned within the hollow is brought into engagement with the stopper pawl. While the operating button is thus temporarily mounted on the operating lever, the operating lever is placed on a support bench with one of opposite surfaces of the operating lever held in contact with the support bench, and a pressure is subsequently applied to an area of the mounting tongue which is substantially aligned with the anchor perforation by means of a presser to thereby form an anchor peg protruding into the anchor perforation in the operating lever.