Make the very trestles shake under the dead, where they lie in their shrouds awaiting the hearses. (20)
Why is this whole war and recruiting thing such a big deal to these people? Oh, yeah: people die in war. This line at the end of the poem makes sure that we don't forget that tiny detail. It also suggests that the war (or war in general) is so momentous that even the dead are shaken by it.