In one sentence, describe what the following article is about:

The white stripes on the Union Jack are not all the same size. The wider white stripes on the side closest to the flagpole should sit on top of the diagonal red stripes. The white stripes represent Scotland's Saint Andrew's Cross while the red ones represent Ireland's Saint Patrick's Cross. A good mnemonic device to use is "wide white top." On the side furthest from the flagpole, the white stripes that run diagonally should be thinner on the top of the red stripe, and thicker below the red stripe. This applies to both white stripes on the side furthest from the flagpole. Saint Andrew's Cross was on the flag first and takes precedence over Saint Patrick's cross. When hanging your flag vertically, the thick white stripe should be on the top of all the other stripes on the top left hand side of your flag. The top edge of the flag should become the left edge of the flag when hanging it vertically. This practice is similar to hanging the American flag, but varies in other countries like Liechtenstein, Slovakia, and Slovenia, where they have different designs for flags hung vertically. Flying the Union Jack upside down is a coded distress signal, and should only be used as such. In the UK, flying the flag upside down may be considered an insult, even if it was an honest mistake.
Look at the white diagonal stripes on the side closest to the flagpole. Look at the white diagonal stripes on the side furthest from the flagpole. Ensure the thick white line is on the top left, if hung vertically. Fly the flag upside down for a distress signal.