Re spoke wrenches, have a look at this picture: http://www.bikesonline.com/product_i...80292_zoom.jpg
The upper socket grabs 3 corners, the lower only 2. I have a set of these, the lower socket is *much* easier to round nipples with. The triangular Park ones suffer from the same problem. Yes - this is caused by me being a careless klutz - the better tool helps me though.