brake line connector

Are you talking about this?

http://www.napaonline.com/Catalog/CatalogItemDetail.aspx/Brake-Hose-Front/_/R-UBK36611_0435793598

The 'tube' end just threads into the wheel cylinder and is tightened; there is a thin copper washer that goes on this end and seals the fitting to the wheel cylinder. The wheel cylinder port where this threads in is angled towards the back of the car and so the right and left wheel cylinders are different. If your wheel cylinder port faces towards the front, you have it on the wrong side.

The rear wheel cylinder ports face straight in towards the center of the car; the rears are identical right to left.