a method of manufacturing a product includes the steps of providing a first and a second product part , each including a structure of fibers ; arranging the first and second product parts relative to one another and against a support ; providing a connecting element having a thermoplastic material ; pressing the connecting element against the product parts to compress the semi - parts between the connecting element and the support and impinging the connecting element with energy , thereby causing thermoplastic material of the connecting element to become flowable , and causing the connecting element to be pressed into the product parts ; and causing the thermoplastic material to re - solidify , thereby connecting the first and second product parts with each other .