(57) A fastening device (10) for locating and fastening a unit such as a window (30, 31) or door (60) in an opening. The device typically includes a pair of upstanding tongues (14,16 114, 116), each with serrated tips (20,22). The device can be made integral with the frame of the window, during manufacture; and with such device fitted the window can be pushed into the opening where it is located, usefully with the aid of an accessory (58) pinned to the wall opening or reveal, without the need for drilling through the frame on-site. In an alternative embodiment the fastening device is integral with the structure defining the opening and the tips engage the unit.
In an alternative application, the device is integrally formed with a door jamb (52), and the door (60) is held in the closed position when the tongue tips enter slots i.e. recesses or apertures (57a, 57b) in an accessory plate secured to the door; the accessory plate has a longitudinal aperture through which a cam (63) projects, the cam being operated by a door handle (62) to lift the tongues out of the slots so that the door can be opened.