In the 1930s, post-frame construction had its start with the development of two key components: availability in rural areas of wood telephone and electricity poles, and corrugated steel sheeting. By using poles embedded in the ground, along with steel roofing and siding, the amount of framing, siding, and foundation material needed to construct a barn was drastically reduced. The columns were literally telephone poles – hence the term 'pole barn'. After World War 2, 'poles' were replaced by solid sawn posts, usually 4×6 or 6×6. The posts were chemically treated to resist decay, greatly increasing the useful life of a building.