The poem is written in blank verse. Frost maintains five stressed syllables per line, but he manages to carry the natural speech-like quality of the poem. There are no stanza breaks or rhyming patterns, but many of the end-words share an assonance (e.g., wall, hill, balls, wall, and well). The language is simple and conversational; no fancy words are used, the words are short and of two syllables (only one word, “another”, is of three syllables), and perhaps this is why the words are so in rapport with one another.
The image at the heart of "Mending Wall" is captivating: two men meeting on terms of neighborliness to build an obstacle between them. This has become a regular procedure for them. Yet nature itself is against the erection of the wall; it hampers the wall from remaining firm. These men replace the broken boulders back on top of the wall, yet ultimately, whether at the hand of hunters, or the invisible hand of nature, the rocks tumble down again. Still, the neighbor persists on continuing with their repertoire. The poem, thus, seems to contemplate on three distinctive themes: barrier-building (animosity, in the broadest sense of the word), the catastrophic consequence of this conduct, and the persistence in this activity regardless of the outcome.
This wall-building act seems ancient and ludicrous, for Frost uses terms such as "spells" and "elves," and the neighbour is described as a Stone-Age man while he builds the wall. The simile Frost uses is very effective as we can vividly imagine the state of the neighbour. Referring him to the dark ages makes us grasp the intensity of his ignorance
But, as we look closely at Frost's poem, we observe that though it is written in a simple and direct manner, it is surprisingly complex. The speaker may scorn his neighbor's unreasonable attitude, but he himself goes to the wall at their annual renovating time to mend the damages that the wall has incurred. Which person, then, is the real wall-builder? The speaker does not necessarily have to go and rebuild his side of the wall. If he does not really want the barrier between them, he should have left the wall as it was, rather than doing the same as his neighbour. But the fact that the speaker does try to convince his neighbour to break down the wall makes him seem a lot better than the stubborn wall-builder. The satirical part of the poem is that the building of the wall is the only time the neighbours interact. Thus, wall-building, for them, becomes more like a social activity.
As a matter of fact, there is a whole lot of purpose and gain in breaking the wall. The bringing down of the wall is probably the key to unification. In fact, nature itself seems to be urging the neighbours to connect with each other by ruining the traditional boundaries.
On a superficial level, Frost seems to be talking about a wall between two typical neighbours but a closer look will reveal that the subject of the poem actually relates to relationships as a whole. The poem also advocates a moral that mankind should be brave enough to elude from the dark and reach out for the enlightenment.