put (your) hand on (your) heart

if you can put your hand on your heart and say something, you can say it knowing that it is the truth.

I couldn't put my hand on my heart and say I'd never looked at another man.

• at the helm
• at the helm of
• at the helm of something
• at the latest
• at the mercy of
• at the mercy of someone
• at the mercy of something
• at the moment
• at the most
• at the outside
• at the point of
• at the point of something
• at the ready
• at the ripe old age of
• at the ripe old age of something
• at the top of agenda
• at the top of lungs
• at the top of someone's agenda
• at the top of the agenda
• at the top of the ladder
• at the top of voice
• at the top of your lungs
• at the top of your voice
• at the very least
• at this stage of the game