This is a replacement of the Y motor mount for the Anet A6.
Check out what version you want. The V2 uses less filament.
You can snap it in as a replacement for the original motor mount. It also acts as a fixing structure for the printer Y backplate. First install the motormount on the backplate and then attach it to your groundplate. When you tighten the Y belt it does not pull on the backplate with the risk of breaking it.
when printed it should fit into the backplate. No sanding needed.