This is designed primarily for cutting the 2020 x-gantry extrusion on the Ender 3 when performing a coversion to the Enderwire.
This can be used for similar 2020 extrusions where you will be cutting it by hand using a hacksaw or other means and need a guide surface to reference against while cutting.
You slide it onto the extrusion with the wider part pointing towards the end of the extrusion you plan to cut. Use the widest part as a flat reference/guide for cutting.
The author hasn't provided the model origin yet.