Diophantus' 20th Problem and Fermat's Last Theorem for n=4: Formalization of Fermat's Proofs in the Coq Proof Assistant

This invention relates to vehicles having parts connected with a sealing spring fastener, which comprises a U-shaped structure, on which an elastic body has been incorporated. The elastic body has a hermetically closed cavity within the U-shaped structure. The sealing spring fastener can form an assembly with an extension of a panel, preferably a plastic panel. The assembly or the fastener by itself can be engaged into the slot of a solid sheet, preferably a metal sheet, in a manner that one side of the sheet is sealed from the other side of the sheet in the vicinity of the slot. In a preferred version, the sealing fastener comprises a substantially non-elastic tough casing around portion of the elastic body in order to avoid rapture during insertion of the fastener into the slot.