Use 'on the level' to express trust in someone's honesty or ethics in business and personal matters. I vouched for her because I knew she was on the level.
Pro Tip 2/3
Casual Speech
'On the level' is more common in casual conversation than in formal writing or speeches. You're on the level with me, right?
Pro Tip 3/3
Affirmation Query
Use 'on the level?' as a question to confirm someone's sincerity or truthfulness. Are you being on the level with me about your experience?