Which of the following is a characteristic of lockbolts?

Lockbolts are a type of fastener known for their strength and security in fastening applications, particularly in aerospace and heavy-duty environments. One of their key characteristics is that they are permanent once installed. This means that, after installation, removing a lockbolt requires special tools and processes, which can often damage the material being fastened if the removal is necessary. This permanence provides a reliable and robust connection, which is critical in applications where safety and structural integrity are paramount, such as aircraft assembly.

The design of lockbolts facilitates a high level of resistance to vibration and dynamic loads, making them an excellent choice in situations where traditional fasteners might loosen over time. Their installation involves the use of specific equipment that combines the bolt and washer into a secure joint, reinforcing the notion that they are intended for long-lasting applications.

The other options do not accurately describe lockbolts. They are not reversible, as they are intended for permanent applications. They're also not installed using soldering, which is irrelevant to the mechanics of how lockbolts function. Lastly, lockbolts are typically made of high-strength metal materials, not plastic. This ensures durability and strength, suitable for the demands of aerospace and similar industries.