Like the eight queens puzzle, you need to place 2 rooks on the board.  But not just anywhere on the board.  The rule is that both rooks may not attack the same square.

How do you place 2 rooks on the board without having them both attacking the same square?

Put a couple of pieces between them

Umm.. no, on an empty board.

You put them right next to eachother 

... right.  You put them next to each other.  They block each other.

Technically, each rook "attacks" the square the other rook is in, but since they don't attack their own square, this is still correct.

You can put up to 8 rooks on an empty board without having them attack the same square.

What about 9 rooks?

Well?  What about 9 rooks? 10 rooks? 11? 12?

a three by three square for nine rooks?

Yep.  For 9 rooks, do a 3x3 square.

What about 11 rooks?

You could also put them on top of each other.

The rook on top isn't attacking any squares.

The rooks have to be on the board.

The rooks on a1 and a3 both attack a2.  The rooks on a2 and c2 both attack b2. etc.

Same problem as above (a1 and a3 both attack a2 etc).

I mean... otherwise you can place 64 rooks on 64 squares...

You could place 64 rooks on 64 squares.

Well, by "attack" I mean "can move to on the next move".

What if 65?Ha

65 is not possible because the board only has 64 squares (duh, lol)

Just a joke