you don't need a nutcracker to open notoriously tough-shelled walnuts. All you have to do is put two walnuts into your hand and make a fist. But, as explained in this video, it's important to align the walnuts properly so that the "seams" touch each other.
Side question: is the shape of the meat of a walnut similar to that of the human brain for the same reason? I asked the smooth-talking BS artist OpenAI and am not satisfied with its answer:
"The shape of a walnut makes it an excellent source of nutrition for the brain, as the many folds and crevices maximize its surface area per volume. This means that each walnut contains a greater amount of essential fatty acids, antioxidants, polyphenols, and vitamins than a plant of a similar size. The similarity between the shape of a walnut and a human brain is thought to be no coincidence, as these nutrients are believed to have helped shape and sustain the evolution of the human brain."
Do you have a better answer?