A method of anchoring a first object in a second object, the method comprising the steps of: providing the first object comprising a first material and providing the second object comprising a second material, wherein the first material is solid and comprises thermoplastic properties and wherein the second material is solid and is penetrable by the first material when in a liquefied state, the second object having an end face, wherein the second object further comprises an opening having a mouth in the end face, the opening having an opening axis and a depth and the first object further comprising an insert portion having a length, wherein the opening and the insert portion are adapted to each other for the insert portion to be positioned in the opening, and wherein said first and second materials constitute at least part of opposite surface areas (18, 19) of insert portion and opening capable of being pressed against each other; anchoring the insert portion of the first object in the opening by transferring energy suitable for at least partial liquefaction of the first material to the vicinity of said opposite surface areas in an amount and for a time sufficient, for liquefaction of the first material and interpenetration of the first and second materials in the vicinity of said opposite surface areas; and stopping the transfer of energy for a time sufficient for the first material liquefied during the step of anchoring to re-solidify; characterized by the further step of applying a clamping force to the second object while the insert portion is at least partially inserted in the opening, the clamping force acting between clamping elements (21, 22, 25) acting on opposing surfaces arranged so that the opening is between opposing surfaces when the clamping force is applied, the clamping force acting in a direction non-parallel to the opening axis. providing the first object comprising a first material and providing the second object comprising a second material, wherein the first material is solid and comprises thermoplastic properties and wherein the second material is solid and is penetrable by the first material when in a liquefied state, the second object having an end face, wherein the second object further comprises an opening having a mouth in the end face, the opening having an opening axis and a depth and the first object further comprising an insert portion having a length, wherein the opening and the insert portion are adapted to each other for the insert portion to be positioned in the opening, and wherein said first and second materials constitute at least part of opposite surface areas (18, 19) of insert portion and opening capable of being pressed against each other; anchoring the insert portion of the first object in the opening by transferring energy suitable for at least partial liquefaction of the first material to the vicinity of said opposite surface areas in an amount and for a time sufficient, for liquefaction of the first material and interpenetration of the first and second materials in the vicinity of said opposite surface areas; and stopping the transfer of energy for a time sufficient for the first material liquefied during the step of anchoring to re-solidify; characterized by the further step of applying a clamping force to the second object while the insert portion is at least partially inserted in the opening, the clamping force acting between clamping elements (21, 22, 25) acting on opposing surfaces arranged so that the opening is between opposing surfaces when the clamping force is applied, the clamping force acting in a direction non-parallel to the opening axis.