Nepal has the only national flag that is not rectangular or square.
Nepal's flag consists of two joined triangular pennants, often described as a double pennon. The upper section contains a stylized moon and the lower section contains a sun. Its crimson red field is bordered in blue, colors associated with Nepalese identity and peace.
The modern constitutional design was adopted in 1962, although the two-pennant form has much older roots in South Asian banner traditions. The flag's geometry is formally specified in Nepal's constitution through a detailed construction diagram rather than a simple length-to-width ratio.
The moon and sun symbolize permanence, with a traditional interpretation that Nepal should endure as long as those celestial bodies. Nepal is therefore easy to identify in collections of national flags: unlike every other sovereign state's current flag, its outline has two points and no four-sided outer boundary.