What does it mean to open a mountain for the elderly?

Generally speaking, it refers to burying an ancestor who moved here, thus forming a family's ancestral grave.

Hakka people in Guangdong usually visit graves for a period of time after beginning of spring. Most areas in western Guangdong did not start sweeping graves until after the vernal equinox, and some places did not start sweeping graves until Chongyang. Every year from the fifteenth day of the first month to the Spring Festival, people will choose the eyes that open new graves on auspicious days, commonly known as "opening mountains". Because only the new graves that have opened their eyes can better feel the power of Feng Shui.