In your Mustang the "battery hold down" is designed to do exactly what it's name implies, to hold down the battery. It does this by wedging itself against the base of the battery and the battery tray thus preventing the battery from moving around while you are driving.
Don't drive your Mustang without a properly secured battery, not only is it much safer but it is required when you take your Mustang to the race track!
Ford Motor Company Genuine Parts, Motorcraft® Parts and Ford and Motorcraft Remanufactured Parts are all excellent choices when it comes to performance, longevity and value for your Mustang or SVT Lightning. And they’re all backed by a Ford Motor Company limited parts warranty*, so you know their parts you use are going to perform like they should. Put the same parts on your Lighting & Mustang that came from the factory!