Protection of Documents

Question: I selected several cells in a spreadsheet and chose the command Extras > Protection > Cell Protected. Nothing happens, all cells can be edited still.
Answer: Protection in documents is a two-step procedure. First you mark elements of the document as protected, just as you did with the cells. Finally, when everything is ready, call Extras > Protection > Lock Document. In the next dialog, you may optionally enter a password. Locking the document activates all protections at once. (Unlocking, it gives you back the entire control you need for changes.)