Albert Barnes Commentary Ecclesiastes 12:3

"in the day when the keepers of the house shall tremble, and the strong men shall bow themselves, and the grinders cease because they are few, and those that look out of the windows shall be darkened," — Ecclesiastes 12:3 (ASV)

The body in old age and death is here described under the figure of a decaying house with its inmates and furniture.

This verse is best understood as referring to the change which old age brings to four parts of the body: the arms (“the keepers”), the legs (“the strong men”), the teeth (“the grinders”), and the eyes.