Daisy, after careful examination of my paws, my humans and I have come to this conclusion: When properly trimmed, the claws on my front paws fully retract into their sheaths, with the exception of my dew claws - they seem to stick out a bit. As for my hind paws, the two toes in the middle seem to be able to fully sheathe their claws, but the other two seem to stick out a little bit.
Despite the fact that a couple of my claws are never fulled sheathed, I still walk silently, creeping around very quietly, not making a noise. This is due to the fact that I have very thick paw pads. Some people say that Sphyhnx look like they are walking on air cushions because of these thick paw pads.
Daisy, I hope that answers your question!
(You can click on the photos above to view a larger version.)