This billhook is used for pruning grape vines.
billhook definition by Webster's New World
Webster's New World College Dictionary Copyright © 2010 by Wiley Publishing, Inc., Cleveland, Ohio. Used by arrangement with John Wiley & Sons, Inc.
a tool with a curved or hooked blade at one end, for pruning and cutting
billhook definition by American Heritage Dictionary
An implement with a curved blade attached to a handle, used especially for clearing brush and for rough pruning.
Origin: bill3 + hook.