Review on Secure your belongings with the 4 Digit Combination Lock - Ideal for School Gym, Sports Locker, Fence, Toolbox, and More by Marcus Merritt

Notice in the close-up that there are only two places where you can insert the shackle. To change the code, use one that opens at a 90 degree angle. Hold it closed with one hand and change the numbers with the other. There is only one place where the numbers are unique, at the end of the lock. The numbers in the middle on the front and back do not match. This leads to a confusing interpretation of which numbers to use where. If you're the only user, this isn't a problem once you know where to put the numbers. This isn't very good if you want to use it for a mailbox. The courier probably won't find out without showing them. Also, the shackle doesn't lock, you have to keep it closed and change the numbers to lock it.