I took my hands off the bars last night and gently pushed on a guy's hip.

Weeknight crit, about mid-race, small pack, somebody had attacked and us weaker riders were tailgunning. We were in a crosswind section, single file against the curb, and one guy was getting popped. He (correctly) pulled out to the left a bit, leaving room for others to pass him downwind / sheltered. But, being on the limit, he was wobbling a bit. So as I come past between him and the curb, he's drifting a bit too close for my comfort so I put a gentle hand on his hip and steered him a few inches to the clear side.

No words exchanged, everybody's fine.