It is a conversion template used when converting an earlier vintage fuselage kit (one meant for a Dynon D-180 EFIS) to a later version designed for installation of a Skyview EFIS.
There is a special plans section (don't remember the # right now) that provides instruction for the use of this template for locating new mounting holes at different location on the fuselage, for installation of the Skyview equipment.
That is a template used for drilling holes. Some of those holes are in the base of the avionics bay. For example, those closely spaced holes making a square are for the USB connector that points down towards your legs.
I forget where all the other holes are located but this isn't a part that actually gets "installed."