When making prusiks, what should be the diameter of the accessory cord compared to the main line rope?

The correct choice indicates that the diameter of the accessory cord used for making prusiks should be in the range of 2/3 to 3/4 of the diameter of the main line rope. This ratio is essential for ensuring that the prusik knot functions effectively.

When the accessory cord is within this diameter range, it allows the knot to grip the main line securely while still being able to slide when under low tension. If the cord is too thick compared to the main line, the knot may not catch properly in a fall or when loaded, compromising safety. On the other hand, if the cord is too thin, it could slip easily or not hold enough friction, which again poses a risk of failure. Therefore, maintaining the specified diameter range is crucial for optimal performance and safety in rope rescue scenarios.

Understanding this ratio is essential for anyone involved in technical rescues, as it directly affects both the reliability of the gear and the safety of the personnel involved in rescue operations.