Better Storage Too offers a bunch of new storage options for Minecraft. You now have more choices with broader storage and security than standard chests. Lockers function like vertical chests with doors on the front. They can be stacked right next to each other unlike regular chests.
You can lock reinforced chests and lockers with a lock and key. The lock is crafted with the key and then that key is left behind in the craft process. That key is the only one that can unlock that lock. So you simply shift+click on your chest/locker and then shift+click to unlock the lock with the key. Plus they take on different colors depending on which ore you use to craft them and they have more storage capacity than traditional lockers and chests.
And crates are an expandable storage system that can be stacked into 5x5x5 cubic piles. They offer a broader capacity but the drawback is that only a random selection can be accessed each time you open them.
There’s also a simpler cardboard box option that has limited uses but can also be used to transport items from place to place. Just load items into the box and break it. You’ll see the items listed in the box’s inventory while carrying it. Then just place it anywhere and you’re good to go!