There are different ways to describe what objects are for:

1. Used + infinitive
2. Used for + gerund
3. Used for + noun

Used + infinitiveUsed for + gerundUsed for + noun
A bag is used to carry things. A bag is used for carrying things.A bag is used for loads that need carried.
A pen is used to write. A pen is used for writing.A pen is used for letters.
Shampoo is used to wash hair. Shampoo is used for washing hair.Shampoo is used for clean hair.
A microwave is used to heat food. A microwave is used for heating food.A microwave is used for food.
This room is used to hold meetings. This room is used for holding meetings.This room is used for meetings.
That bucket is used to collect rainwater.That bucket is used for collecting rainwater.That bucket is used for rainwater.
This camera is used to watch the front door. This camera is used for watching the front door.This camera is used for the front door.
Scissors are used to cut things. Scissors are used for cutting things.Scissors are used for cuts.
Banks are used to save money.Banks are used for saving money.Banks are used for savings.
Cars are used to go from one place to another place. Cars are used for going from one place to another place.Cars are used for journeys.