what are season trade lines and do they work and what ones are legit if they work?

Question

i read that they can raise your credit line

Answer 1

Seasoned trade lines are accounts that have been opened for years.

If you know of anyone that has a card that is in good standing, no lates, no overlimits, and low utilization, you could ask them to add you as an authorized user.
You should also request to the card company that they report on your credit.

If you are added to an account as an AU, it would increase your score since you would receive all of the history of the card.