A method for joining two objects by anchoring an insert portion provided on a first object in an opening provided on a second object. The anchorage is achieved by liquefaction of a thermoplastic material and interpenetration of the liquefied material and a penetrable material, the two materials being arranged on opposite surfaces of the insert portion and the wall of the opening. During the step of inserting the insert portion in the opening and/or during anchorage a clamping force is applied to opposing surfaces of the second object to prevent the second object from cracking or bulging.