– The image shows you the word GRINDSTONE with the two letters N in red. Below each letter N there is a letter O, also in red. If you read vertically, you figure out that the N and the O make the words NO. So there are to NOs to GRINDSTONE. Remember the word – image puzzle has a strong basis in phonetic reading, so two NOs actually are NOSE.
– To keep your “nose to the grindstone" means to work hard, constantly, driven by an inner feeling of responsibility. It means, in short, to be dedicated to your work in a conscientiously manner.