A method of mechanically securing a first object to a second object, wherein the first object has a thermoplastic material in a solid state, the second object has a generally flat sheet portion having a second object edge. A third object is provided and arranged to provide an assembly including the first, second and third objects, in which assembly the second object edge is in contact with the thermoplastic material. Mechanical vibration energy is coupled into the assembly by means of a vibrating tool until a flow portion of the thermoplastic material due to friction heat generated between the second object edge and the thermoplastic material becomes flowable and flows around the second object edge to at least partially embed the second object edge in the thermoplastic material and the third object is caused to be embedded at least partially in the thermoplastic material of the first object.