A posthole digger is a tool used to create holes in the ground in which to insert posts for fences, signs, and more. This tool is also known by several synonyms that refer to its purpose or method of use. One common synonym is a hole digger, which accurately describes the tool's primary function. Another is an auger, which refers to the spiral shape of the digging blade attached to the end of the handle. A third synonym is a clamshell digger, which describes the action of the two-bladed digging tool that opens and shuts like a clamshell. No matter what you call it, a posthole digger is a necessary tool for any outdoor project that requires sturdy and secure posts.