I am working on converting a Sims 4 bookcase that has 2 sides with books.
When I test the object in-game with access to both sides, I instructed one Sim to study from one of the sides, and the other Sim from the other side - both used the same side.
When the bookcase is placed front of the wall (one side only showing), both Sims use that side.

In the slot file, there is only one routing - is that the reason?
If so, would the values of the routing change for the other side?

I have attached the zip.file - please note I have not added the container slots yet and not fixed the books yet.

Thank you in advance for any help you can offer.

Update: 28/01/2024
I had tried having a look at the Very Mysterious Looking Shelving (Apartment Life EP), to see if I could use this as it is double-sided; however it is made up of a front, back plus the two parts of the door frame.
I also looked at the CRES info to see if that could help me and tried copying some of it on my bookshelf CRES, but Sims still continued to go the front of the bookshelf to get their books.

The problem cloning is the size difference, the door not required plus I am unable to split my bookcase into a back and front.

Thank you in advance for any assistance.

Have you looked at this thread?
https://modthesims.info/showthread.php?t=592649

Hello @omglo
Thank you for this link.
I will have a go at trying to make the bookcase a standalone object and follow the other guidelines too.