Let's begin with some simple rook forks. Ask traditional questions: What Black pieces are loose? The knight and rook. What checks can White give with his rook? Rd1 and Rb7. We seek a match between these possibilities and find it in Rb7+, a move that wins the knight after Black moves his king. Absorb the position visually. The spectacle of the Black king and knight both on the penultimate rank should immediately suggest tactical possibilities. They aren’t on squares of the same color, so a double attack by a knight or bishop won’t work, but they are easy prey for a rook (or queen).