These can also be used to create individual characters and, if known, represent an alternative such as using a visual character map, such as KCharSelect, the character map on the KDE desktop environment on my Linux machines.
KCharselect with the left-hand guillemet selected
So what’s the keyboard shortcut alternative for French quotation marks?
On Linux, most special characters can be inserted into a text editor or office package using the AltGr key plus one or two other keystrokes. If you have the patience to learn them, they can save a lot of time.
For the left guillemet, AltGr+z produces «.
For the right guillemet, AltGr+x produces ».
As you can see, it’s a lot quicker than using a GUI-based alternative.
* = I’ve always used a standard EN-GB keyboard layout.