Can I say "great at" instead of "great for"?

Rebecca

Using "great at" instead of "great for" would change the context of the sentence! "Great at" is often used when a person is good at doing something. The phrase "great for" is used when an object has a good use for something. Ex: This tool is great for screwing nails in securely. Ex: James is great at fixing cars. Ex: This light is great for seeing at night.