Which of the following is an example of a lifting device?

A shackle serves as a crucial lifting device in rigging and lifting operations. It is designed to connect various components of a lifting system, such as slings, ropes, or chains, allowing for the secure and safe attachment of loads. Shackles come in different types, such as screw pin or safety pin, and they provide a means to create a link in the lifting system that can handle dynamic loads and stresses.

In contrast, a wrench is a tool used for turning nuts and bolts, which does not have a functional role in lifting loads. A safety harness is a personal protective equipment item designed to secure the worker and prevent falls while working at heights, but it does not do anything to lift or hoist loads. Similarly, a hard hat is used for head protection but does not contribute to lifting devices in any way. Therefore, the shackle is the most appropriate answer as it directly relates to the lifting of loads in rigging applications.