What is a block-and-tackle end line attached to?

The correct answer is that a block-and-tackle end line is attached to the upper block with more sheaves. In a block-and-tackle system, the upper block is typically fixed and serves as the point where the pulley mechanism is anchored. It contains multiple sheaves (pulleys), which significantly affect the system's mechanical advantage. By attaching the end line to the upper block, the design maximizes efficiency in lifting or moving loads, allowing for easier handling of heavier weights.

Understanding the configuration of the block-and-tackle system is vital, as it directly influences the effectiveness and safety of the lifting operation. The upper block's design with multiple sheaves provides a way to distribute the load more evenly, reducing strain on the system components and enhancing overall stability during operation. This arrangement is fundamental in many applications, from construction to specialized lifting equipment.