Which component would best be described as a small pin used to secure a bolt?

The component that is best described as a small pin used to secure a bolt is the cotter pin. Cotter pins are widely used in various applications to prevent nuts and bolts from loosening or becoming dislodged. They are inserted through a hole in the end of a bolt or shaft and then bent over to hold it in place, thereby ensuring that the assembly remains secure during operation. This is particularly important in mechanical settings where vibrations or movement could cause components to loosen.

The other options represent different components that serve distinct purposes. For instance, a grabhook is a type of hook that is generally used for securing loads, while a keeper can refer to a device that retains another part in position, and a yoke typically refers to a frame used for joining two connected parts. Each of these components plays a unique role in their respective applications but does not serve the specific function of securing a bolt as effectively as a cotter pin does.