Securing a second object to a first object

A method of manufacturing an assembly, comprising the steps of:

• providing a first object,
• wherein the first object has a proximally facing surface portion,
• wherein the first object has an indentation having a mouth in the proximally facing surface portion, the indentation being manufactured by pre-shaping, the indentation having a sidewall;
• providing a second object that has a lateral outer surface portion,
• wherein at least one of the lateral outer surface portion and the sidewall comprises a thermoplastic material;
• bringing the second object in contact with the first object so that the lateral outer surface portion is in physical contact with the sidewall;
• coupling mechanical energy into at least one of the first and second objects so as to cause energy absorption due to friction between the lateral outer surface portion and the sidewall, until a flow portion of the thermoplastic material becomes liquefied;
• and
• letting the flow portion re-solidify, whereby the flow portion secures the second object to the first object, and
• wherein the flow portion interpenetrates the side wall of the first object to form a positive fit after resolidification.