Rear brake flex hose question

Yes. On the old cast dual Master Cylinder, The square black piece claps to the top of your master cylinder with chains that come with it. Then you add brake fluid to the tank. Then you pump the handle till the gauge shows 3-5 PSI, you then crack each caliper/wheel cylinder bleeder till all the air is gone. I did the whole brake system on my 68 Barracuda with every piece on it new and a dry system. After I was done I had uded a half of quart of fluid including what it took to fill the system. I'll let a system sit maybe a hour and crack every bleeder just to make sure. Theres no bench bleeding the MC either.