The two part joint, mortise or whole and tenon or protrusion, is the very definition a peg and hole. The best expression of this is a joint, a connection so tight, so exact, there’s no need for a fastener, e.g. a nail or screw. At the other end of the spectrum you have the proverbial, square peg and round hole.

Image via brewminate.com

Not exclusive to Mission style furniture, many cultures and woodworking styles have used this joint for thousands of years. It’s so strong that it can be used in the construction of a house. A friend of mine growing up lived in a house her parents built that used mortise and tenon construction. There were no nails used anywhere in the house. The joint was pinned with wooden dowels but no nails or screws.