A method of mechanically connecting a connector to a first object, comprising the steps of: - Providing the first object, the first object having an opening; - Providing a first connector element, a second connector element, and thermoplastic material in a solid state; - Placing the first and second connector elements (4, 5) relative to the opening; - Causing energy to impinge on the thermoplastic material, until at least a flow portion thereof becomes flowable and flows relative to the first and second connector elements (4, 5) until it is in direct contact with both, the first connector element and the second connector element; - Causing the thermoplastic material to re-solidify; - Whereby the re-solidified thermoplastic material locks the first and second connector elements (4, 5) relative to one another to yield a connector assembly comprising the first connector element, the second connector element and the thermoplastic material; and - whereby the connector assembly is anchored in the opening by the thermoplastic material or by the locking of the first and second connector elements or both, characterized in that one of the connector elements (4; 5) comprises a head portion (41; 51), and the other one of the connector elements (5; 4) comprises a foot portion (51; 41), in that in the step of placing the first and second connector elements relative to the opening, the one connector element (4, 5) with the head portion (41; 51) is placed from a proximal side so a that a portion reaches into the opening and the head portion (41; 51) remains proximally thereof, and the other connector element (5; 4) is placed from a distal side so that a portion reaches into the opening and the foot portion (51; 41) remains distally therefrom, wherein the second connector element comprises an outer tube portion, wherein in the step of placing the second connector element is placed relative to the first connector element so that the outer tube portion encompasses a section of the first connector element, wherein the flow portion includes material that flows until it is in an intimate contact both, with an inner surface of the outer tube portion and with an outer surface of the encompassed section, and wherein at least one of the following conditions is fulfilled: • the step of placing the first and second connector elements (4, 5) comprises placing a thermoplastic tube element between the outer tube portion and the encompassed section, and wherein in the step of causing energy to impinge, the thermoplastic tube element is caused to become flowable at least in part until an axial extension thereof is reduced and the thermoplastic material is in intimate contact with at least an inner surface of the outer tube portion and an outer surface of the encompassed section; • the step of placing the first and second connector elements (4, 5) comprises placing an outer thermoplastic tube element encompassing the outer tube element, and in the step of causing energy to impinge, the outer thermoplastic tube element is caused to become flowable at least in part until an axial extension thereof is reduced and the thermoplastic material is in intimate contact with at least an outer surface of the outer tube portion and an inner surface of the opening. - Providing the first object, the first object having an opening; - Providing a first connector element, a second connector element, and thermoplastic material in a solid state; - Placing the first and second connector elements (4, 5) relative to the opening; - Causing energy to impinge on the thermoplastic material, until at least a flow portion thereof becomes flowable and flows relative to the first and second connector elements (4, 5) until it is in direct contact with both, the first connector element and the second connector element; - Causing the thermoplastic material to re-solidify; - Whereby the re-solidified thermoplastic material locks the first and second connector elements (4, 5) relative to one another to yield a connector assembly comprising the first connector element, the second connector element and the thermoplastic material; and - whereby the connector assembly is anchored in the opening by the thermoplastic material or by the locking of the first and second connector elements or both, • the step of placing the first and second connector elements (4, 5) comprises placing a thermoplastic tube element between the outer tube portion and the encompassed section, and wherein in the step of causing energy to impinge, the thermoplastic tube element is caused to become flowable at least in part until an axial extension thereof is reduced and the thermoplastic material is in intimate contact with at least an inner surface of the outer tube portion and an outer surface of the encompassed section; • the step of placing the first and second connector elements (4, 5) comprises placing an outer thermoplastic tube element encompassing the outer tube element, and in the step of causing energy to impinge, the outer thermoplastic tube element is caused to become flowable at least in part until an axial extension thereof is reduced and the thermoplastic material is in intimate contact with at least an outer surface of the outer tube portion and an inner surface of the opening.