Provided are devices and methods of applying a film (120) to a first panel of a vehicle wherein the first panel is connected to a second panel of the vehicle by a joint area containing a ditch portion (52) that is recessed relative to the first panel. The method includes the steps of placing into the ditch portion (52) an elongated jig (100) that comprises a shim (102) extending continuously along the length of the ditch portion (52), the shim (102) protruding above a height of the first panel, applying the film (120) to the first and second panels such that the film (120) extends over the elongated jig (100), and then using a tool (122) to apply pressure against the film (120) and toward a cutting edge of the shim (102) along the length of the shim (102) to trim the film (120) along a peripheral edge. The elongated jig (100) can then be removed from the ditch portion (52), and the peripheral edge of the film (120) adhered to the ditch portion (52).