The title, "Bit parts," points to small pieces, and the poem is built from three of them: feet, hands, and a strange discovery at the end. The first two stanzas praise the body's quiet knowledge. Feet "know how / to love the land," as if walking were a kind of affection that needs no thinking. Hands, meanwhile, are "having a way to be rich" and "turn to design," which suggests that skill and making are a form of wealth that has nothing to do with money.
Then the tone shifts. The speaker finds "a cod's head / in my manuscript." It is a surprising, almost comic image, and it's hard to say exactly what it means. Judging by the contrast, the writing may have picked up something raw, fishy, and physical from the world, or the speaker may be amused that the body's earthy intelligence has turned up in their written words. The mood is light, curious, and a little playful, with real warmth toward the physical and the natural.