Frost's narrator says that the "buzz saw snarled," using a metaphor (implied by the verb snarled) to compare the saw to an angry and unpredictable animal. A metaphor compares two unalike things, claiming that one is another without using the words like or as. Animals, like dogs or cats, tend to snarl when they are very upset, and this high level of emotion (with limited means of expression) often result in some kind of violence—like biting, an action that draws blood and harms the one bitten (like the saw does when it cuts the boy). Later, the narrator says that
At the word [supper], the saw,
As if to prove it knew what supper meant,
Leaped out at the boy's hand, or seemed to leap—
Here, the narrator personifies the saw, giving it the ability to "know" what a word means and to "leap," or seem to leap. Personification is the attribution of human qualities to something nonhuman. By giving the saw life—either as an angry animal or a person with intention and understanding—Frost gives it a sinister quality. Anything that seems unpredictable, knowing, and dangerous would be.
Frost uses several techniques to ensure that the saw appears sinister and threatening in "'Out, Out--.'" First, "snarled and rattled," the sounds made by the saw, are repeated; they suggest a dangerous animal with "snarled" as well as the mechanical nature of the saw with "rattled." Will the beast attack? Is the saw somehow loose? The saw, furthermore, is given life with the verse, "as if to show saws knew what supper meant, /Leaped out at the hand, or seemed to leap--." Here the saw is depicted as a hungry creature that seems to attack the boy's hand, viewing it as supper.
The dangerous image of the saw is also suggested in the beginning of the poem with Frost's description of the setting: "from there those that lifted eyes could count / Five mountain ranges one behind the other/ Under the sunset far into Vermont." The scene foreshadows two images: first, the five mountain ranges suggest five fingers, red under the sunset--a bloody hand. Second, the sharp teeth of the saw are similarly suggested by the mountaintops glowing red under the sunset.