Which of the following is a common type of non-threaded fastener?

A common type of non-threaded fastener is the snap ring. Snap rings are used to secure components on a shaft or within a housing and do not have threads. They fit into grooves and provide retention for parts, making them effective for applications where components need to be held in place securely without the use of threaded fasteners.

In contrast, bolts and nuts are threaded fasteners designed to create a clamping force when tightened together. Washers, while they may be used in conjunction with bolts and nuts to distribute loads, are also not standalone fasteners on their own but typically accompany threaded connections. This highlights why snap rings are distinct among fasteners, as they serve a specific purpose without the necessity of threads.