This mounting plate allows you to fit a simple momentary-contact push button into a standard 2.25" round hole in an aircraft instrument panel. In this particular case, it is designed to fit the square push button that comes with the TruTrak Vizion autopilot kit that activates its "emergency level" function.

When installing this in an instrument panel, you can use either Tinnerman clip nuts, self-locking nuts, or just machine nuts. Typically #6-32 screws are used for securing gauges into instrument panels.