The blank had a small "D" shaped 1/2" knot in the top and a heavy curl figure on the side. When I started turning, the curl disappeared and the knot emerged (complete with bug holes - I filled the bug holes with CA glue so that the bowl would be functional). As I hollowed out the bowl, the little knot moved slowly accross the bowl and turned out to be the other side of this large knot. I think that it was a branch that broke off then the tree grew around it hiding the knot.