The poem uses dialect to convey the tone and mood. It also uses refrain, "ain't been no crystal stair" as emphasis. It adds imagery to the reader, "splinters" "tacks" "boards torn up" "places with no carpet" and "bare" which rhymes with stair. After "and places with no carpet on the floor-"
"bare"
The "-" adds a pause, adds emphasis to the exasperation and gives the reader time to take a breath.
"I'se a been a-climbin on" shows strength in the face of hardship. It contributes to the author's purpose by conveying the tone and mood of a working class, black person facing struggles of poverty and misfortune.