The tile floor felt cool under his back and buttocks.

The floor under her back was hard and a little cold.

He could feel the museum's tile floor under his back.

"Help me," Grace said, moving to push an arm under his back.

At the same time, the door squirmed under my back.

There was the yielding surface of a bed under his back.

He put his hand under Data's back and felt for the switch.

She struggled to get the strips under his muscular back.

"I could feel some of it under my back ."

Thrust built up under his back, held for a time, then eased to almost nothing.