have something under your belt
成語所屬單字belt
have something under your belt — 慣用語
1. to have already gained an experience, qualification, or achievement that you can
1.慣用語
釋義
（經驗、成就）已收入囊中；已具備
to have already gained an experience, qualification, or achievement that you can rely on later.
例句
With three marathons under her belt, Mira felt ready for the Tokyo race.
Once you have a teaching diploma under your belt, schools will take you seriously.