Post hole digger
A post hole digger is used to dig narrow holes to install posts, such as for fences and signs.
There are different kinds of post hole diggers. The one on this picture is twisted into the ground in the open position until the blades are buried. At that point the handles are pulled apart to close the tool and grab the chunk of soil loosened. They are then pulled out of the ground with the chunk of soil. The process is repeated until the hole is deep enough or until the handles can no longer be pulled apart. This is one of the weaknesses of this kind of post hole digger.
There are also auger type post hole diggers.