It quite possibly involves having some folds in the cards, which increases their strength.
Index cards have many different uses. One can be to write notes on when making a speech, oral presentation or debating. You can use them to categorise different items and hold them in order to create a database. You can make a 'to-do' list on index cards. They can be used as flash cards to learn words or other information.
I use index cards to study my vocabulary.
Because they are commonly used to make indexes for topics. ie. You would use "index" cards to make an alphabetical index of all the books you've read, guys you've date, etc.
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You can have index cards as flaps and put the date on the front and when you flap it over, info is on the back
You can make index cards stronger by using thicker cardstock or laminating them for added durability. You can also reinforce them by adding tape along the edges or corners to prevent bending or tearing. Additionally, storing them in a protective container or box can help maintain their strength over time.
The two cards that you typically use will be for bibliographical information; and notes.
bibliographical information; notes
Each player receives 13 cards at the beginning of a bridge hand, so bridge cards are narrow to make it easier for a player to hold the cards in their hand.
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You hold up your index and middle finger like a Y and say Peace
The question isn't entirely clear. Are you writing notes on index cards, or do you want to make notes about some sort of index? Please write a new question stating this more specifically -- if you are asking about some sort of index you need to state which index you need to write notes about.