This chapter focuses on the impact moling technique. Impact moling is the formation of a bore by the use of a tool that comprises a percussive hammer within a torpedo-shaped cylindrical steel body. The hammer may be hydraulically or pneumatically powered. The technique is usually associated with non-steered or limited steering devices, which have no rigid attachment to the launch pit and rely upon the internal hammer action for forward movement to overcome the frictional resistance of the ground. During operation the soil is displaced, not removed and normally no lubrication or fluids are used to assist in the creation of the bore. It is probably the most commonly used of all the items of trenchless installation equipment with many thousands of machines in operation worldwide. It has been extensively adopted by utility companies and their contractors as it offers a very cost effective method of installing small to medium diameter pipes, ducts, and cables for a broad range of utilities including gas, water, electricity, telecommunications, and sewerage. The technique is generally unsteered and is, therefore, most suitable for short drive lengths such as simple road crossings and the installation of service connections from the distribution network to the end user.