"Pulled the rope" vs "pulled at the rope."

Solution 1:

The comments are so fun, and already getting upvoted (mutual admiration society?). Anyway, if the rope was actually already secure, you could say "pulled at", but more likely you'd say "tugged on". This doesn't necessarily involve moving the rope at all. (by the way, "pulled at" sounds particularly ineffectual, like "pawed at".) However If the rope was not already secure, the person could "pull" the rope, or "pull on" the rope, to tighten it so that it was secure. He could do both: "...pulled the rope into a knot, then tugged on it to make sure it was secure"