The middle marks are the semicolon, the colon, and the dash. Changing punctuation is mostly a matter of raising or lowering it in the hierarchy. When the punctuation is raised, the writer creates more separation and emphasis , and vice versa. The highest punctuations, the section gap, paragraph break, and period, are fairly obvious and usually give writers little trouble. The three in the middle, the semicolon, colon, and dash, are also relatively easy once a few simple rules are understood.
Colons signal a move from general to particular.
Dashes sometimes perform a function opposite to colons, taking a sentence from particular to general. More often, dashes are used for emphasis. Usually a comma could be used in the same place, but the writer chooses to raise the punctuation for greater emphasis. My father doesn't say what Doc said back some grunt or mumble through his mustache but later, on Blood Road in his oxcart, Doc was jumped by three men wearing bandannas, like the outlaws they had read about in dime novels. I've always been hesitant about heights not actually frightened, only concerned and reluctant about climbing, a controllable vertigo.