This "circle thingie" intrigues me more every day. Just when I think I have something figured out (and I usually do), I find there's another perfectly reasonable way to look at the exact same motion.
Let's start with the name - wa*uke. It translates as circle*block. Aaarrrggghhh!!! This was a Chinese "thing" until someone on Okinawa chose to call it by what it's supposed to be, or so they thought. If only that person saw what I do with circles in Seisan. Out go the lights! If only they saw the way a great grappler or aikidoka uses circles to manipulate and gain advantage and even throw.
It's just a circle, damnit!
But let's get back to the very, very narrow subject of using it as a circle "reception" (call it block if you must) for a linear attack. It's a great thing for this fighting system. The open hands separate us from the closed-fisted fighters that must interrupt what they do to grab. When we "receive" a technique, we are put in a position to get hold of an attacker and begin to control their center. Good stuff...
There are two very, very different schools of thought that I see on this thing.
* Many people see the circle as the first thing that intercepts a linear attack. They like the fact that they're contacting with the broad side of the forearm.
* Some folks (myself included) see a parry of some sort as the first likely contact with the linear attack. Say what you will about the value of your super-dooper circles. I don't see squat for circles when I watch people spar. My esteemed colleague Mr. Khoury went so far as to suggest that perhaps the true meaning and value of the circles was in the reverse circle, and that Okinawans hid the fact they were practicing tode in their back yards (see Gary's sparring video, available on George's online store). You see...our sparring buddies just don't use the darned things. What's up with that? But they DO parry all the time. Sure, sure, talk to me about how parrying uses the palm and that can't happen during the dump, and yada, yada, yada. I don't think so. One of the most natural things people do is to parry. Westerners in particular have had perhaps tens of thousands of balls thrown at them in their lifetimes. And you know what? You don't have to parry with the palm. Miss, hit with the forearm instead, and you are still good. THEN when you've deflected the attack ever so slightly and you're on the way back to a chamber, you deftly hand the technique over to a softer circle that is better able to concentrate on snatching this thing.
Trust me - it works. I have exercises where I have people drill this face-to-face ad nauseum. Do it outside and you parry down the center line - just like the wauke at the end of Sanchin. Do it inside and you parry a little farther - the distance you bring your hand across in the main body of Sanchin when chambering. It's the same thing you do in kata, thousands and thousands of times. It works.
Under the dump? I think so.
* But then... I was working with George on kotekitae in a class some time back. (Yes, I listen to my teacher now and then...
). Anyhow, he has this way of shifting his body orientation ever so slightly to and fro, and all of a sudden this circle can move a Mack Truck. Find that groove, and it's simply amazing. But...you are doing a very strong motion with that circle. You can practically rip the person's arm out of the socket w/o ever grabbing on to it. I've gotten to the point now that I have to tone it down a bit in kotekitae. 
Need more big brutes to pick on. 
But you see...the more you focus on making that circle something that moves a truck, the less likely (IMHO) you're going to be able deftly to grab that thing you're working with. It's possible, for sure. But a football receiver with "great hands" has an amazing ability to hold the hands soft until the point of contact. In a flash, their hands become Venus Fly Traps. Same with basketball, baseball, etc. It's a feeling thing, and you can't feel right when you're exerting too much force. A receiver can't catch a ball that he's beating. He's receiving the thing, after all...
But you sure can move people like midgets with that power circle.
Sometimes a guy just wants to let that testosterone rip... 
But...I was working with Gushi sensei the other week. And Gushi has this way of doing circles big, slowly, and with open hands until the end. Then he curls them. Damn... It's just like what I've been trying to teach my black belts about doing that 4-times move in Seiryu. Big, soft, slow, smooth, open....FOCUS!!!. Well, not exactly like Gushi sensei and the simple "wauke," (circle thingie...), but... It made me think I might be thinking right.
Maybe...
- Bill
P.S. I'm not looking for anyone to solve this riddle for me. I'm happy with its complexity, and hope the plot gets thicker!
The circles one makes in various ways can be done with weights,of course, such as,dumbbells, wrist weights that are strapped one, glove weights,etc. or they can be done as some school of Chinese Kungfu do, holding sacks of rice(small ones), sacks of sand, sacks of metal filings or shot,etc. There are also other devices. The reference to brick laying reminded me of this. Various ways of grasping things and also not grasping things are important it would seem. Some of the arnis movements seem to have come, according to some schools of thought, from hitching harnesses to horses,the movements, of which concealed techniques! So the point that some daily work tasks concealed karate tactics and movements is not far-fetched as it might seem to some. The modern varieties of karate are more 'OPEN' and the subtle movements usually ignored sometimes in favor of more spectacular motions,etc. The daily work of peoples in indigenous,primitive, and 'traditional' cultures often gave them a tenacity that is lacking in modern day practitioners! The old-timers in early history called it ,'raw-hide' toughness! This intensity-tenaciousness seems to be lacking in many ways, even though some practitioners are powerful and massive,etc.
