How does a double purchase system affect the movement of battens?

In a double purchase system, the movement of battens is designed to be half of the movement of the arbor. This means that for every inch the arbor moves, the batten moves only half an inch. As a result, this design allows for a greater mechanical advantage—it enables the operator to lift heavier loads with less effort. Therefore, the correct answer indicates that the battens indeed move slower than the arbor.

In contrast, the other choices do not accurately represent the mechanics of a double purchase system. The system is characterized by this specific ratio of movement, which is crucial for understanding how weight and force interact in stage rigging.