On 356b t-6 and 356c models the battery is held down with the rubber strap; there is a hook molded into each end. The battery has a black plastic cover. This strap hooks to the back wall and goes over the cover and hooks to a loop on the lower bracket.
Once again, you can have a factory original tool kit for your 914. Admittedly you don’t get many tools for the money, but what a great concours display item!