One of the most common traps in chess is known as the Noah's Ark Trap. It often occurs in the opening, particularly with the opening known as the Ruy Lopez or Spanish Game. In this trap, white's light-squared bishop is trapped on b3 by black's pawns. Here is an example of how the Noah's Ark Trap can result:
1. e4 e5
2. Nf3 Nc6
3. Bb5 a6
White's third move is the final move of the opening known as the Ruy Lopez or Spanish Game. Black's response is the most common response in this opening. It's called "putting the question to the bishop" because white must decide whether to capture the knight with his bishop (exchange variation of the Ruy Lopez) or keep his bishop by moving it to a4.
4. Ba4 Nf6
5. 0-0 d6
Though black's knight attacks white's pawn, he prefers to develop by castling rather than defend his pawn. Black decides not to take the pawn but move the queen pawn to open a diagonal for his light-squared bishop.
6. d4 b5
7. Bb3 Nxd4
8. Nxd4 exd
Here white is down a pawn but must not take black's pawn with his queen. To do so is to fall victim to the Noah's Ark Trap.
9. Qxd4 c5
10. Qd1 c4
White's bishop is now trapped on b3. After move 8, white is down a pawn but has a powerful bishop on b3 and a castled king. If white wishes to avoid the loss of a pawn at this stage of the game, one option is to capture black's knight with the bishop on move 4 and the other is to play d3 on move 6 rather than d4.
The Noah's Ark Trap is a trap that has been used many times in chess against an unsuspecting opponent. Though it often occurs in the opening of the Ruy Lopez, it can occur at any stage of a game and with many other openings as well. White needs to be careful to make sure that the light-squared bishop doesn't get trapped on b3 by black's pawns.