I don't understand how Rooklyn and Queens are indestructible structures? A rook can attack the structure and take pieces off the board if it's ok with sacking i

I don't understand how Rooklyn and Queens are indestructible structures? A rook can attack the structure and take pieces off the board if it's ok with sacking itself. Edit: nevermind, the secret is revealed at the beginning of the paragraph >I prevented pieces from capturing pieces on other boards. so normally it's not an indestructible structure, but with that rule it is. Got it.