When examining connotative language in any poem, it is essential to delve into the use of language as trying to convey something beyond dictionary meaning. Connotative language enables the poet to use language as a portal of relevance and purpose. In this light, the words identified for their connotative element and the images that Frost employs in the poem are meant to explore the thematic conditions in the poem.
One example of connotative language is seen in the very title. "Mending" is connotative because of how it functions in the poem. On one hand, it can be seen as representative of the repairing of the wall. It is the annual ritual in which the neighbors participate. They fix the wall that has been damaged, and repair the gaps that have formed as a result of the natural and human constructed conditions that surround the wall. The use of "mending" speaks to the actual repair, the work in which both men speak to the rocks that form the wall: "Stay where you are until our backs are turned!" When we delve into the word, it reflects something like sewing, as in to mend a dress. The notion of sewing something up can mean closing it off, no longer allowing space to present itself. Such a connotation connects to the refrain of "Good fences make good neighbors" where the mending of the wall closes up any possibility of connect between both men.
The image of the wall itself becomes a dominant element in the poem. It represents a boundary, a line that cannot be crossed. Frost is skilled enough to understand how boundaries are an intrinsic part of the human condition. Boundaries come to define an individual through external marking of a line or point that cannot be crossed, only approached. The image of the wall represents this in the poem. It is a boundary that marks out the potential for human endeavor and, in this case, human contact. This is seen in the question posed about walls, in general: "Before I built a wall I’d ask to know/ What I was walling in or walling out." The wall is symbolic of how some boundaries cannot be overcome and that one's mode of being in the world is heavily influenced by the boundaries that exist in it.
In describing how the neighbor moves in his placement of the stones, Frost suggests that he moves in "darkness." The use of "darkness" contains layers of connotative meaning. "Darkness" can reflect the lack of clarity about the motive regarding the fence, the external boundary. The "darkness' of not being certain is evident in this use. It can also represent a form of closing off, as in the more gaps that are filled, the darkness the wall presents as a looming figure. The "darkness" could also represent the neighbor's state of mind, close off from thinking any other way outside of "Good fences make good neighbors." It is a form of darkness meant to keep the speaker in the dark as to his neighbor's life and consciousness. In keeping consistent with the idea of wondering what one was "walling in or walling out," the darkness could represent a type of force that is being kept in or kept out by the wall. The "something" that opens the poem is contrasted with the "darkness" at its conclusion. The connotative image of darkness towards the conclusion of the poem helps to "illuminate" a different aspect of the ritual, the wall, and the boundaries it demarcates.
Finally, the word "neighbor" is significant to the poem. It represents the wall's purpose, as well as the critical element in the father's maxim. The neighbor could simply be the person who lives on the other side. Yet, it could also come to represent the forces that exist outside of ourselves. Frost is posing the fundamental question of how we appropriate boundaries and the impact this has on the people who exist on the other side of them, our "neighbors." What individuals do in facing the boundaries in their own lives and whether or not these objects that demarcate end up making "good neighbors" is a critical question to ask. The traditional notion of a neighbor is one who does not really adhere to boundaries. When examining the standard use of "neighbor," one is confronted with the exact opposite of isolation, separation, and distance. Yet, the use of the term in light of boundaries is of vital importance to the maxim that helps to shape the poem. It helps to maintain the civility between people who are different and opposites to one another. The reader is left to question how boundaries might actually save and preserve the "neighbor" relationship, in the process reconfiguring how one sees the "neighbor" as both image and verbal pattern of recognition.