Which lines from "Mending Wall" best indicate that the speaker is amused while repairing the wall? We wear our fingers rough with handling them. Oh, just another kind of out-door game, No one has seen them made or heard them made, But at spring mending-time we find them there. And he likes having thought of it so well He says again, “Good fences make good neighbours.” We have to use a spell to make them balance: “Stay where you are until our backs are turned!”

We have to use a spell to make them balance: "Stay where you are until our backs are turned!"

Explanation:

Robert Frost's poem "Mending Walls" presents a contradicting life of humanity, with the metaphor of two neighbors mending walls to stay connected and peaceful. This contradiction also refers to society as a whole, with the ironic act of coming together to mend the fence which makes them have a better bond.

The speaker narrates how he and his neighbor had to come together to get the fence mended. But despite the 'barricade' of the fence, it was this necessity of making boundaries that break boundaries. And his amusement can be seen in the lines "We have to use a spell to make them balance: 'Stay where you are until our backs are turned!'"  

we need the speech to be able to answer your question, reply with it and i'll reply with the answer.

some sort of sound device i believe.