Which device is used to move loads such as steel plates or concrete panels without the use of slings?

The correct choice is a lifting clamp, which is specifically designed for securely gripping and lifting loads such as steel plates or concrete panels without the need for slings. Lifting clamps provide a stable means of handling heavy materials, allowing riggers to lift, transport, and position loads safely and efficiently.

These devices typically have a mechanism that creates a strong grip on the material when weight is applied, ensuring that the load remains secure during lifting operations. This ability to directly attach to the load makes lifting clamps particularly advantageous when slings might not offer adequate support or when the shape of the load does not accommodate traditional rigging methods.

Other options, such as hoisting straps and load chains, are typically used in combination with slings for lifting but do not function as standalone solutions for moving loads without slings. A rigging block is primarily a component used in pulley systems and does not engage with the load directly like a lifting clamp does. Thus, the lifting clamp is the most suitable device for moving loads without slings in various rigging applications.