: In hardware and construction, "tornillos de cabezas huecas" refers to socket head screws or hex screws . These are specialized fasteners with a recessed (hollow) drive area, commonly used in machinery.
Interestingly, neuroscience validates the feeling. When we are sleep-deprived, stressed, or multitasking, our prefrontal cortex (the "CEO" of the brain) goes offline. In those moments, we are functionally hollow: Cabezas Huecas
In many Latin American and Spanish cultures, calling someone a Cabeza Hueca is often playful rather than vicious. It is the affectionate scolding a grandmother gives a grandchild who left their keys in the fridge. : In hardware and construction, "tornillos de cabezas