Nut (fruit) usage of the term is less restrictive, and many nuts (in the culinary sense), such as almonds, pecans, pistachios, walnuts, and Brazil nuts, are not nuts in a botanical sense. Common usage of the term often refers to any hard-walled, edible kernel as a nut. A nut in botany is a simple dry fruit in which the ovary wall becomes increasingly hard as it matures, and where the seed remains unattached or free within the ovary wall. Most nuts come from the pistils with "inferior" ovaries (see flower) and all are "indehiscent" (not opening at maturity). True nuts are produced,
Square nut yellow, plain, zinc clear, tin and cadmium, among others. Most can meet either the ASTM A194, ASTM A563, or ASTM F594 standard. Early nuts were made of wood and were used with wooden pegs. The square shape made it possible to form a tool in order to tighten nut in place. Later wooden fasteners were replaced by steel ones, and modern nuts are forged from steel stock bars and used along with steel bolts. Square steel nuts were common on machinery of the late 19th through mid 20th century. Today hex nuts have displaced them. One reason is that a