Abstract: An alignment device for a firearm, the alignment device being mountable on said firearm and being shaped to define, in at least one mode of use, a sighting aperture located adjacent a base of the device such that, when the base is positioned, in use, on a surface of the firearm, the sighting aperture is located adjacent said surface. The device comprises a body with an elongate aperture having a longitudinal axis extending in a first direction; and a cover mountable on the body and including at least one aperture that is at least partially in register with said elongate aperture during use. The body and the cover are slidable with respect to one another in said first direction. The device allows firearms, especially shotguns, to be correctly fitted to a user for various modes of shooting.