How to create a relationship between two tables that allows duplicates?

I am writing an mvc .net application to learn. I have a table for cards and one for decks. I want to make a "deck" able to have cards added to it. I can do this as a one to one.

I assume I need a third table or a join of some sort.

What I need to be able to do is add duplicates of cards to the deck. Essentially the cards library would only list a card once, but a deck could have 3 of a specific card in it. Also, a card should be allowed to be listed in multiple decks. If you are familiar with MTG cards this will probably make more sense.

Sorry if this is a beginner question. Any assistance would be greatly appreciated. :)