"the keepers of the house shall tremble … and the grinders cease because they are few" (12:3). What are the keepers, the grinders and the silver cord?

The chapter doesn't say what each picture stands for, so these notes won't either. What it does say is where the pictures sit. They hang on "Remember also your Creator in the days of your youth, before the evil days come" (12:1), and in the middle of them it says in plain words, "because man goes to his everlasting home, and the mourners go about the streets" (12:5). After the silver cord, the golden bowl, the pitcher and the wheel (12:6), it ends with "and the dust returns to the earth as it was" (12:7). So in the WEB the pictures stand in one long sentence that begins with "the days of your youth" and "before the evil days come" (12:1) and ends with "the dust returns to the earth" (12:7). The keepers, the strong men, the grinders and "those who look out of the windows" (12:3) are not explained anywhere in the book, so these notes leave each picture as the text gives it, and let 12:5 and 12:7 say plainly where the pictures lead.