What should be used where there is an unequal strain on the two parts of the line?

Racking seizing is specifically employed to handle situations where there is an unequal strain on two parts of a line. This technique provides a secure binding that can stabilize and distribute the load effectively across the line, preventing slippage or failure due to uneven tension.

In contrast, the other options serve different purposes. Throat seizing is typically used to secure the throat of a sail or a gaff but does not address strain distribution. The bowline knot is a reliable knot for creating a fixed loop at the end of a line, but it does not provide stabilization for uneven tension across two parts. The square knot, while useful for tying two ends of a line together, isn't designed to accommodate or compensate for unequal strains.

Utilizing racking seizing in situations of unequal strain ensures that the integrity of the line is maintained and helps to prevent accidents or equipment failure.