Quote Originally Posted by sperk
How would you say "arm in arm"? (Walking side by side with your elbows interlocked and the back of your elbow touching your partner's body.)

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Рука об руку

And it's usually pronounced like a single word:

Рукаобруку. (bold о is under stress). Separate pronounciation is possible:
Рука об руку (but I've never heard the stress falling on either of у's in the last word).