A post pounder, also known as a fence post driver or post knocker, is a tool used to drive fence posts into the ground. Typically, post pounders are comprised of a metal pipe with one closed end and one open end. For stability, most post tools of this nature have handles or grips on either side of the pipe. The open end of the post driver is slipped over the top of a fence post and repeatedly slammed against the post to drive it into the ground. Pounders are sold based on weight, post diameter, and power options including manual, pneumatic, or hydraulic.
Manual post pounder tools are usually weighted with concrete or solid steel at the closed end to provide additional driving force. Users hold the side handles or grips to lift the heavy pounder up, then slam it against the top of the fence post. Most manual post pounders are intended for use with metal t-posts, such as those used for cattle, horse, or electrical fencing in agricultural settings. Additional applications suitable for a manual post pounder include posts for dog kennels, street signs, and other small projects.
Large fencing projects call for a hydraulic or pneumatic post pounder. Power or hydraulic post drivers operate on gas, propane, or other fuel. Pneumatic post pounders use an air compressor to power the tool. Rather than manually lifting and slamming the post pounder, users of power-driven post knockers need only set the tool on top of the post and hold it straight. In the case of pneumatic tools, air pressure forces the post pounder down against the fence post, driving the steel post deeper and faster than a manual tool.
Hydraulic and commercial grade pneumatic post pounder tools are capable of driving almost any type of fence post. While manual and small pneumatic post drivers are generally limited to driving posts with diameters of 2 inches (5.08 cm) or less, larger tools can accommodate much larger posts. Additionally, commercial post drivers can also accommodate posts of different materials such as steel, wood, or composite. Internal pistons drive the posts into the ground, rather than lifting the entire tool.
Professional and commercial grade post driving tools have more wearable internal parts and require more maintenance. Lubricants such as piston oil and hydraulic fluid require regular monitoring and refill. Maintenance and replacement parts aside, the ability to deliver more than a thousand blows per minute and accommodate posts up to 4 inches (10.16 cm) in diameter compensates for the additional maintenance. Automatic stability control in the form of internal balancers provide hands-free operation.