The upward and downward interlocked triangles are called the Sudarshana Chakra. It is a symbol of strength and is Vishnu’s weapon. The Sudarshana chakra was made by the architect of gods, Vishwakarma.
His daughter was married to Surya the Sun, but found him to be too hot and couldn’t go near him. Eventually the Sun agreed to allow her father to put him on a lathe and pare him down to a fraction of his original brilliance.
Vishwakarma took the left over bits and made the Sudarshana Chakra for Vishnu, the Trisul (trident) for Shiva, and the Pushpa Vimana, an aerial car that ended up in the hands of Ravana although Rama acquired it after that war in Lanka.