In the first 5 lines of the poem "The Mending Wall" by Robert Frost, Frost indicated that the earth doesn't like a wall, because the wall keeps crumbling on her, and doesn't stay intact. It is almost like the earth is shrugging the wall off of her surface. This causes a lot of damage to the rocks, creating "gaps even two can pass abreast," and this damage is what Frost and his neighbor go out to repair. In lines 5 and 6, Frost refers to the damage done to the wall by hunters that he has to repair. He clarifies in lines 7-11:
"Where they have left not one stone on a stone,
But they would have the rabbit out of hiding,
To please the yelping dogs. The gaps I mean,
No one has seen them made or heard them made,
But at spring mending-time we find them there."
In these lines, Frost says that the hunters, in order to help the dogs get at the rabbits who have hid themselves in gaps in the wall, pull the stones apart, leaving "not one stone on a stone" to help them out. The gaps that the rabbits hide in seem to always mysteriously appear; "no one has seen thme made or heard them made," but every year as he and his neighbor go walk the fence, they find them.
I hope that explanation helps to clear things up for you; good luck!