Last thing to be done to setup my ss/fixie is to cable up the front brake. I have bullhorn handlebars, and one time trial lever on the end, and one cross lever. So I need to cut two pieces of housing: one from the TT to the cross, and one from the cross to the front brake. I am, at the moment, out of ferrules. With a clean cut and ground end on the housing, what are the ferrules doing for me? Do I need them?