Hi Tina,

About your question,

a/an = is usually used for non-specific and generic cases.
the = is usually used for specific cases (specific common nouns, singular or plural, and before proper nouns that are plural or to name oceans, rivers, regions, or newspapers).

In your answer:
"make the furniture"
We were talking about what a carpenter does "in general" so it is best to use: "make furniture"

I hope this helps you in learning how to use articles (the,a/an).
See you in class! :)

~*Teacher Vhielle*~