Some people may become confused with the use of under and below, especially since they seem to be highly similar to each other. Under and below both refer to being lower or less than something else, but the way that they are used can be different. Under is a term that is commonly used more than below. You can say “under the table” when you are referring to an object that can be found just below the table.
You can say “look up below” when you are trying to inform those who are from below to look up and avoid potential items that may come in contact with their heads. If you are concerned about which word you should use more, you can just choose under.