Diagonal Cross, also known as a Saltire, is an X-shaped cross that is commonly used as a symbol of Scotland. It is also used in heraldry and religious symbolism. The term 'diagonal cross' refers to the shape of the cross, which is formed by two lines that intersect at a 45-degree angle. The Saltire is one of the oldest flags in the world, and it has been used as a symbol of Scotland since the 12th century.