The term 'hourglass fill' is used to describe the process of filling an hourglass-shaped container with SAND. The two crossword solutions for this term are 'SANDS' (5 letters) and 'SAND' (4 letters). SANDS refers to a type of granular material composed of finely divided rock and mineral particles, while SAND is a naturally occurring granular material composed of finely divided rock and mineral particles. Both SANDS and SAND can be used to fill an hourglass-shaped container.