Devices and methods for improved installation of trim, such as trim boards, to a building substrate. An alignment device configured for use with a nail gun is sized and shaped to facilitate repeatable and accurate angled nailing of trim boards at a desired nailing angle and height relative to a building substrate. The alignment device is sized and shaped to stably seat within an angle between a trim board and a building substrate such that a nail gun user can repeatedly drive nails at a regular angle and height through the side of the trim board and into the building substrate to nail the trim board to the building substrate without requiring the user to measure and/or visually determine the height and angle at which the nail will be driven. The alignment device includes a spacing section having a length that determines the spacing between the muzzle of the nail gun and the nail entry point, an entry angle section that determines the angle at which the nail will be driven, and an entry location section that determines the height at which the nail will be driven.