Its a simple poem about the dangerous job of repairing the barbed wire in front of the trenches during World War I. This had to be done at night otherwise the wirers would be shot. Occasionally the enemy (Germans in this case) would fire up a flare to illuminate No Mans Land, the land between the allied and German trenches. That's how poor Hughes was caught out in the poem. The best thing to do to avoid detection in poor light is to stand absolutely still - the eye is designed to detect movement. At the end he says sarcastically well at leats the wire is up, eventhough he died.

-metaphors, sound imagery,