Well, this may not be all that interesting to you if you are not as obsessed as I am with closing the knee joint comfortably and safely, and all the little actions that go into Karandavasana. But maybe some of you may find this little insight to be useful at some point (or not), so I'll just relate it here.
First, a little back-story. If you have been following my posts about splitting and closing the knee joint (see this post and this post), you will know that one of the issues I have been struggling with is how to close the knee joint and get into padmasana upside down without using the hands. For anatomical reasons that I don't fully understand (Frank has suggested that this may be due to lack of quadricep flexibility, but I don't think this is true in my case: I can bring the entire soles of my feet to the mat in Bhekasana), whenever I bring my right heel to the back of the right thigh to try to close my knee joint, it never closes completely, and I have to recruit my hands to get the heel to cover that last half an inch or so in order to close the knee joint completely.
Well, a couple of weeks ago, I discovered a little trick to get around this problem. Suppose you are in shoulderstand, and you are trying to close your right knee joint in preparation for Urdhva Padmasana. You bring the right heel to the back of the right thigh. If you are like me, there will be a gap of about a half-inch or so between your heel and the back of the thigh. This is where the trick comes into play: Instead of trying to squeeze the heel directly towards the thigh (this won't work anyway, if you are me) or recruiting your hands, you kind of move the right knee out towards the right while inching the right heel further into the left hip crease. The funny thing is that doing this action somehow does the trick: Somewhere between the outward motion of the right knee and the inching of the right heel towards the left hip crease, the right knee joint actually closes!
I don't know if anybody else out there would find this little trick useful (or would even care; this probably won't even make Grimmly's list of yoga party tricks...) But remember, you are dealing with a yoga-geek here ;-)