Building brake lines........need some help

[NW Task Force]

Ok folks,

I went out and bought several 3/8-24 inverted flare nuts and 3/16" steel brake line. The thing I am trying to learn/understand is why the master cylinder brake line connection bosses are so much larger than the 3/8-24 IV nuts? It looks like both bosses are different sizes.....what is the reason for this? What exactly do I need to adapt the 3/8-24 IV nuts to the master cylinder? I found some old fittings laying around in my toolbox. These fittings were used to "cap off" master cylinders for testing. It appears one fitting is roughly 1/2" and the other 7/16". I am new to the world of building brake lines......need some basic knowledge of fitting sizes and such.