OBSTRUCTION going into 2nd???

[PFISTO]

Ok here is the play, R1 on 1st stealing 2nd on the pitch. F6 covering the throw, comes down with his right knee 75% blocking 2nd base. When would you call obstruction??? Would F6 have to have the ball in his glove before he blockes the bag, Could he be in the act of catching the ball, would it make any difference where the throw came in ie close to the bag or near his right shoulder. Just wondering what your thoughts are on this. Rule 2.22.1 defines Obstruction High School rules