So I planned on replacing the brake lines on my truck today since they were looking pretty corroded. My dad came over and we got started, tore off the old lines and went to advanced to get new ones. Come back start installing the new ones, get to the last one, a stupid 1 foot long piece on the left rear is not threading into the 4 way junction it comes from. Take a close look at it, threads look fine...hmm. find the part that came out, it goes in just fine, we look at the 2 the one end is bigger. Why oh why do you design something where one fitting in the whole damn system is bigger than the rest? So tomorrow I'll go get a new fitting for that one end of that one line.

I'm an engineer but I can't come up with a good reason why one would design something this way. Makes no sense to me. Maybe someone here can enlighten me, but stupid designs like this seem all too common whenever I work on cars.