With those same Boots of Lead, again, (line 11)
This seems to us to be the most painful line in the poem. Boots of Lead? Come on! This woman can't catch a break here. The suffering in this poem mostly comes on two fronts: noise and weight. If we imagine her as the floor or as beneath the floor, these heavy boots are pressing down from above. What does "again" mean here? Has she gone through this whole experience some time before in her life, or is she only referring back to the "treading" of the first stanza?
And Being, but an Ear, (line 14)
Throughout the poem, the speaker has been in a passive position, with people literally walking all over her. Now, she reworks this passivity on a cosmic scale. She's just an ear inside a giant, universal bell. If you've ever put your ear next to a gong or the opening of a large bell as it rings, you'll know that this is not a pleasant position to be in.
And hit a World, at every plunge, And Finished knowing–then– (lines 19-20)
Like a match of interstellar bumper cars, the speaker collides with a different "World" as she falls. What does "at every plunge" mean? Does she go through multiple falls, or is her fall broken up into different stages? The phrase "finished knowing" has been likened to blacking out after a lot of painful. It's another example of the mind and body only being able to take so much.