In robert frost’s “mending wall,” the neighbor tells the speaker that good fences make good neighbors. what does he mean by this?

What the speaker means by saying that 'good fences make good neighbors' is that he'd rather see a fence than his neighbor. He wants to have as little interaction with his neighbor as possible, which is why he wants a fence between them so as to keep their interaction to a minimum. The protagonist believes this fence is unnecessary, as it will create an isolating barrier between them, but the speaker still wants to have it.