This adapter allows easy attachment to the Valve Index's controller (Knuckles). It is intended to be a base for other designs, rather than being useful itself.

I used a 0.2 mm clearance which works well on my printer but might not be give the desired fit on others, so be gentle to avoid scratching and round over all edges with a file. Print in the orientation shown in the included picture. The nose of the adapter's "boot" tip has been modeled with a steep enough internal angle that it should not require support, so block them there as it would be hard to remove them in such an enclosed spot.

The adapter is held on with the Knuckle's strap adjustment button. Feed the end of the strap's cord through the appropriate hole and then press the strap button to slide the adapter on. The button has some side-to-side wiggle, so make sure it has aligned properly with the hole. Using the corner of a credit card from the edge works well to push it over into place. It should result in the adapter being solid but with the strap adjustment still working properly.