It is a stacking aid for the MakerTom battery boxes. This means you can stack the boxes on top of each other without them slipping down.

The stacking aid is glued to the bottom of the battery box using 3D printing glue.

In order to stick the stacking aid, the AA battery box is filled with batteries.

Then the non-rounded side of the stacking aid is wetted with a little glue.

In order to stick the stacking aid, the AA battery box is filled with batteries.

Then the non-rounded side of the stacking aid is wetted with a little glue.

Then place the stacking aid with the rounded side down in the box filled with AA batteries.

Now place the 2 boxes centered on top and let it dry briefly.

Don't wait too long so that both boxes stick to each other due to overflowing glue.

Therefore use only a little glue. After taking it down, press the stacking aid a little and you're done.

Have fun with it.