This helps keep your lead screw(s) vertical. There is a cutout in the center for a bearing.
One file slides into the aluminum extrusion, the other mounts onto the bolt holes on top of the gantry.
I designed this for the Longer LK5 Pro, but it should work with other printers of the same style, e.g. Ender 3 series, Comgrow, Elegoo, etc.
The author hasn't provided the model origin yet.