What is a "shackle" used for?

A "shackle" is primarily used as a device for restraint, typically employed to confine a person or an object, usually by fastening it around the ankle or wrist. The term is often associated with physical restraint, indicating a mechanism that restricts movement, often linked to historical contexts, such as prisoners being shackled. This contextual understanding highlights its primary purpose, which is to limit freedom of movement, making option B the correct choice.

While the other options pertain to different categories, they do not align with the primary function of a shackle. For instance, a decorative item focuses on aesthetic appeal rather than functionality, gardening tools relate to plant care, and weapons serve as instruments of harm or defense. Therefore, only the understanding of a shackle as a means of restraint appropriately characterizes its intended use.