Talk:Lieutenant's Chainsaw/@comment-5180556-20141101115339/@comment-17834624-20141128135958

That's the rev trigger for the chainsaw. A chainsaw has three components to working it; the hook, which readies the chainsaw, the safety, which (if you pull the trigger while it's on) prevents it from revving the chainsaw, and the trigger, which revs the chainsaw. The chainsaw has the safety behind the blade, and then the handle.

TLDR; Mercen-X is right.