I accidentally designed my item holder in a way that the insert's flat side is at the bottom, which on my honeycomb wall causes the holder to be askew in a 30-degree angle when installed.
This adapter rotates the slot 30 degrees, allowing you to install your holder upright without completely re-printing it if you're in the same situation.
The adapter does slightly increase the gap between the wall and attachment, so if that's important to you, you should keep it in mind.
Edit: It seems like I have installed my honeycomb wall in an incorrect orientation, which is the culprit of this issue (thanks Balu for pointing it out). This adapter still works as described (rotates the slot 30 degrees), but make sure your wall is in the correct orientation (where the slots have a flat side at the bottom) before trying this or any other fixes.
The author remixed this model.
Modified the empty insert to work as an adapter for rotating the slot 30 degrees.