Hand impact drivers are fantastically simple tools. The first time you see one, you will wonder how it could possibly work---but work they do, and amazingly well. There's no other tool that handles the job these tools were intended for. There's a great deal of control with a hand impact driver, unlike a power impact tool. If you can hold the tool and swing a hammer, you can use this very affordable and indispensable tool.
Install the bit adaptor and bit or the appropriate socket on the tool.
Grasp the tool firmly in your left hand (if you're right-handed).
Engage the stuck screw or bolt.
Apply downward pressure, while at the same time attempting to turn the impact driver in the direction you want the screw to turn. This is generally counterclockwise to loosen, clockwise to tighten.
Strike the top of the impact driver with a hammer. Wear heavy gloves to minimise injury if you accidentally hit your hand with the hammer.
Continue striking the tool while applying pressure and turning force until the bolt is loosened enough to use a faster tool, such as a socket and ratchet wrench.
Tighten a bolt or screw in the same manner, and by applying a turning force in the opposite direction.
Hand impact drivers are great for loosening stuck screws but, to help prevent damage to the screwhead, be sure to clean all dirt from the screw slot.
As with all tools intended to be struck with a hammer, be sure to wear safety glasses when using a hand impact driver.