arm in arm—with one’s arm under or around another person’s arm:
- Sally and Joan were laughing as they walked arm in arm down the street.
hand in hand—
1. holding hands:
- Molly and her stepmother wandered about in the gardens hand in hand, like two babes in the wood.
2. in close association:
- It provides a unique mix of a professionally educated workforce working hand-in-hand with volunteers.