Beneath it by a wide culvert the Deeping-stream passed out.
Orcs had crept like rats through the culvert through which the stream flowed out.
There was for a while a lull in the assault, since the attempt to break in through the culvert had been foiled.
They have crept in the culvert again, while we talked, and they have lit the fire of Orthanc beneath our feet.
They gathered such small boulders and broken stones as they could find to hand, and under Gimli’s direction the Westfold-men blocked up the inner end of the culvert, until only a narrow outlet remained.