I’ve had enough of my neatly packed groceries ending up all over the trunk by the time I get home, apples, and potatoes rolling into unreachable dark corners, and the bread and eggs somehow ending up under the milk. And heavy stuff can slide around and actually cause damage. Happily the solution is pretty simple, thanks to the fact that the carpet in my trunk (and the trunk of most cars) sticks well to the hook side of Velcro.  Applying it to a few simple braces makes for a quickly adjustable dividers that can corral whatever you put in the trunk.