1. Open a file with Vim 2. While having a cursor in a first line you want to comment - enter visual mode (Ctrl + V) 3. Select with arrows a block of code you want to comment. 4. Select Shift+I to put editor in INSERT mode then insert `#` (or any character you like). This will add hash to the first line. 5. Press Esc and it will insert `#` to entire block you have selected