It seems that I'm going to have to replace the main front-to-back brake line in my beetle. I have a bit of a problem thought that's confusing me.
In the following two photos, the left brake line on the left is stub line that connects the right rear brake hose to the slave cylinder on that wheel. The right one is the end of a piece of brake line that I bought at the parts store. The end is called a "double flare". I don't know what the left one is called.
Here's the socket in the master cylinder that the main brake line has to screw into. The bottom of the hole is bevelled down, to match the convex flare in the left brake line.