In case of engine block crack this is one of the very few repair options you have. If it is done correctly can be class approved also.
You might never have to do it your self but it is nice to know how is done.
In this video you need to have the sound on. Unless you have x-Ray vision you can only hear the surging not see it.
In this one, you can both hear and see the damage. Ch. Eng nightmare!!!