Ultraminimalist Wall Mounted CD Holder Rack Variable Length Customizable

Extendable.  Modular.  Minimalist.  Wall Mountable.  Each standard section holds a dozen CDs.  Or twenty slims.  Or 6 double disc. I use IPS WELD-ON to join the parts.  Modular.  Double Disc and Half Slim jewel case options.  DIY customizable uncut segment.

Each segment is approximately 8 inches.  To make a 4 foot rack you need to print approximately 6.  With top and bottom screw mounts, it will go over by about 3 inches, so a total of 51ish.

Screw is M4 countersunk but can also be hidden by a dowel plug.  This is approximately the size of a drywall or a #8 T15 screw.  You could hang on a nail but it may not be as sturdy. There are two options for this, one prints without support, the other is mushroom shaped and requires supports.  I recommend screwing it in at both ends.

While you may get away with < 20% infill, I'm probably going to test out 100% and other settings.  My prototypes will be in PLA+ but (probably) ultimately I'm going to print it in PETG for my own needs.

Print segments on the side for the most vertical strength, requires supports.  Print on back if you are confident with your material, no supports required.

Be advised.  It's minimal, so it isn't locking your CDs in all that mechanically.  It will hold them, though. If you attach to a non-anchored bookcase that is easily bumped, it might be catastrophic for your collection.  Probably won't work well in an earthquake zone, but then again I assume you're not going to be mounting them on a wall. If you double it up it might be more apt at holding discs, but probably not helpful when mounted all that much.

You can also just print the middle sections and glue them together to make something that lays flat or at a grade.  If you double this up you get a nicer desk-style CD holder.  You can screw it into a desk or table or piece of wood (or not).