The suit is nothing without a person to go inside it. Throughout the poem, the speaker's body serves as a guide for the suit, filling (line 3) and shaping (line 20) it. But the speaker isn't the only one with a body. In lines 10-11, the speaker's legs enter the suit's "hollow" legs; the suit becomes an outer body for the one inside of it. In line 12, the suit "embraces" the speaker, which would definitely require both of them having arms. As the speaker wears the suit, it grows to fit him, and even becomes as worn (line 29) as the speaker is growing. Both of their bodies change with age, and they become the same body in the end, buried together under the ground in line 70. In these final lines, the suit and the man have become one, united forever.