We love IKEA. We never have trouble with parts missing from our purchases, so we were really surprised to find an endcap missing from a räcka curtain rod.

I could have contacted IKEA.  They have great customer service and probably could have sent me a replacement, but where's the sport in that?  Much more interesting to design and print my own repair.

The endcap is a simple plug, with a threaded hole for the finial to attach.  The plug has a small bump along the cylinder that helps hold it in place.

Of course, I forgot that every rod has two diameter rods -- an inner rod nests within the outer rod, so that the total length is adjustable.  I was missing the cap for the larger rod, but the first time through I took measurements of the inside, smaller rod.  So here are the replacement parts for both. 

Next step: design and print some more interesting finials.  Moose antlers, anyone?

https://www.littlechip.me/2019/04/ikea-racka-endcap/