The current flag of Saudi Arabia has been in use by the Kingdom since 1973. The flag has a green background to represent Islam and a sword to represent strictness in applying justice.
The most notable part of the flag is the Arabic inscription which is the Islamic declaration of faith, also known as the shahada, which states “There is no god but Allah; Muhammad is the Messenger of Allah" . Because the flag has such a sacred inscription on it you won’t see it on t-shirts or other souvenirs because that would be considered disrespectful.
The flag is manufactured with identical obverse and reverse sides, to ensure the
reads correctly, from right to left, from either side. The sword also points to the left on both sides, in the direction of the script.
In fact, due to the inscription, the flag is never flown at half-mast because this is considered blasphemous and is illegal in Saudi Arabia. There has even been controversy when the flag was printed on soccer balls made by FIFA, as kicking the flag with your foot is a huge offense. In the early 2000s the US army in Afghanistan handed out soccer balls adorned with flags to children which led to protest.
The flag also cannot be hung vertically as this would mean the writing is read on its side.