Which of the following is NOT a type of common steel buttplate?

The correct answer is composite buttplates, as they do not fall under the category of common steel buttplates. Composite buttplates are typically made from materials such as plastic, polymers, or other composites and are often used in modern firearms and sporting equipment to reduce weight and improve ergonomics.

In contrast, checkered steel buttplates, steel-trap buttplates, and skeletal buttplates are all made of steel and serve different functions. Checkered steel buttplates provide improved grip through texture, helping to prevent slippage when shouldering a firearm. Steel-trap buttplates are designed to accommodate a trapdoor mechanism, often used for storage of ammunition or cleaning supplies, while skeletal buttplates are lightweight and minimalistic, usually offering a reduction in weight while still providing effective shoulder support. All these options highlight the traditional use of steel in buttplate design, differentiating them from the composite alternative.