Answer: Both use everyday language.
Both Robert Frost's "Mending Wall" and Carl Sandburg's "Frost" use everyday language. This is their main similarity. This type of vocabulary allows them to convey their ideas in a way that is accessible to everyone. It is also a characteristic that sets them apart from other more traditional poets.
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Bandwagon.
Loaded Words.
Testimonial.
Name-Calling.
Plain Folks.
Snob Appeal.
Misuse of Statistics.
Transfer.
The answer is assonance i believe (sorry if im wrong)