Don't bother, after arguing with Dyson about this part on the phone 3 times I have decided to go smash my Dyson vacuum with a Sledge Hammer and to buy a real Vacuum instead. They have lost me as a customer forever over a 12 cent plastic part. By the way, here is Schematic that actually shows the part. It is the Cyclone Release Catch. I did find one local vendor that can get me the part, but I still think I would rather video tape myself destroying the vacuum.
While this is necro-posting, I'll give it a try anyway. In the linked diagram, part 49, the "Cyclone release catch" on our DC14 no longer grips the canister correctly. Customer service thinks it's this catch that's at fault. OK, I have one on order. I looked at the enlarged photo, on the SearPartsDirect site, of the switch cover. I now am confident that "all" I need to do is pop the cover, pull the catch, put in the new catch, and jam the cover back on. Easy-peasy right? The devil is in the details, of course. What do I need to do to release what seem to be two locking catches on the switch cover?
For the record, neither Dyson or SearPartsDirect show the catch, but the customer service person was able to identify the part and even got the color right (purple, not red). I'll know in a week if my faith is well placed.