The invention provides a method of anchoring a connector in a first object, wherein the first object is a lightweight
structural element having a first outer structural layer and an inner lining layer, wherein the first outer structural layer is thinner and denser than the inner lining layer, wherein the connector comprises a
solid thermoplastic material, the method comprising the steps of: - bringing a distally facing
coupling face of the connector into contact with an
attachment site of the first outer structural layer; - displacing a portion of the first outer structural layer at the
attachment site relative to the inner lining layer by applying a first pressing force to the first outer structural layer and causing the first outer structural layer to be pierced at or near the
attachment site; - applying a second pressing force to the connector and transferring energy into the connector, thereby moving the connector in a distal direction relative to the first object until a flow portion of the
thermoplastic material is liquefied and caused to flow into an interpenetrating structure of the inner lining layer; - stopping the
energy transfer and allowing the flow portion to re-solidify.