Answer: The buzz saw in Robert Frost's "Out Out" symbolizes the sudden cruelty life can inflict.
Explanation: In the poem, the boy dies by blood loss when his hand is severed by a buzz-saw. The use of personification describes the buzz saw, an inanimate object, as "snarling" and "leaping" out of the boy's hand, but the saw is not at fault for the boy's death, it is the result of him doing the work of an adult man.
The saw itself is a tool, but is also the extension of the person using it. In a way, it's a deadly tool depending on who uses it, and how qualified they are to use it.