Which of the following methods involves using a single wire for safetying?

The method that employs a single wire for safetying is the one referred to as single wire wiring. This technique involves using a single strand of wire to secure fasteners or components, typically by looping the wire around the item to be safetyed and twisting it to ensure it remains tight. This method is especially useful in situations where space is limited or when you need to provide a lightweight solution for safetying.

Single wire wiring is often favored in applications where the vibration or movement can potentially loosen fasteners. By having one wire securing the joint, it prevents the fastener from backing out while minimizing additional weight. It's a straightforward and effective method of ensuring components remain securely fastened, making it essential knowledge for aviation structural mechanics who work with various aircraft components.

In contrast, other methods such as double twist wiring involve using two strands of wire twisted together, cotter pin insertion requires a pin that fits through a hole in a fastener, and lock nut fastening utilizes a nut designed to resist loosening. Each of these methods employs different techniques or materials and are utilized based on specific application requirements and safety regulations within aviation maintenance practices.