Decorative hollow concrete blocks - GIF

[Jon]

This reminds me of a trick that sailing voyager Bernard Moitessier warned about in his book The Long Way.

In impoverished nations, people would rob boats of their food supplies by sneaking onto the boats, and opening the canned foods from the bottom, emptying the can, and then returning the empty can to the shelf. Moitessier mentioned a couple who embarked on a long passage only to discover halfway through that all of their cans were actually empty.