Which of the following is a mechanical fastener used in woodworking?

The answer is correct because all the options listed can be considered mechanical fasteners used in woodworking, albeit in different ways.

A glued joint relies on adhesive properties to bond pieces of wood together, but it is often complemented by mechanical means to provide initial alignment and stability until the glue cures.

A staple is a common mechanical fastener in woodworking, providing a secure attachment of materials like plywood or fabric to wooden frames. It effectively holds pieces together by penetrating the surface.

A wood dowel serves as a connecting element that fits into corresponding holes drilled into two pieces of wood, providing strength and stability. Dowels can enhance the mechanical connection between wood components, making them a trusted choice for joining.

Hence, all these methods contribute in various ways to securing wood elements together, solidifying the conclusion that they constitute mechanical fasteners in woodworking.