The ‘sad’ in the name is the old English word for solid, and it was, a very heavy type of flat iron pointed at both ends, used to press heavy woollen fabrics. It would be heated over the open fire or range and held over a damp cloth, the steam penetrating the wool to set the work, shrinking it to fit or flattening the natural springy fibre into a flat state. Not that you’d use them now, even with a range to heat them – but the double ends would be quite useful sometimes.
Flat iron
A solid, pressing iron, made of cast iron with a flat triangular shaped plate. Once fully heated – over hot coals or the range – it would be used to press household linen and clothing, always over a damp muslin cloth. The steam had the same effect as a modern steam iron and the cloth protected the fabrics beneath from excess heat and iron marks. The laundry of a large house would have several irons in different sizes and weights which would be used with different types of fabrics. I seem to remember that some were filled with hot coals and other with water for weight and, or, longer lasting heat.