|This article does not cite any references or sources. (August 2008)|
A square nut is a four-sided nut. Compared to standard hex nuts, square nuts have a greater surface in contact with the part being fastened, and therefore provide greater resistance to loosening (though also greater resistance to tightening). They are also much less likely to become rounded-off after repeated loosening/tightening cycles. Square nuts are typically mated with square-headed bolts. Square nuts are used along with flat washers in order to avoid damage from its sharp edges and helps to increase the strength of the fastener.
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.
Commonly used in furniture as a blind nut, they are also used in rail channels in order to prevent turning of rail when pressure is applied. They are also used to make perfect foundation in metal channels for hidden fasteners.