The concept of "off" is typically contextual. Just like the word "on," the sign for "off" is often demonstrated through the action of one thing being taken off another, or by showing the spatial relationship between objects.
However, if you're referring to turning something off, such as a light or a machine, there's a specific motion:
If you're trying to show the position of one object in relation to another (like taking a book off a table), you might use the actual objects or representative handshapes and their positions to each other.
Again, ASL heavily relies on visual-spatial representations. Prepositions and similar concepts often rely on the positioning of signs and the use of space.
If you're looking to learn more sign language, check out our other ASL resources. We constantly update these resources to provide you with useful new signs you can use in your day-to-day life.