Directional boring or Hydraulic Directional drilling (HDD) is a method that utilizes a guidance system to direct a drill rod through the ground. Once the drill rod is at the exit pit, a reamer and the product are attached to the drill rod. The product is then pulled by the drill rod back into the ground and back to the HDD rig.
Directional boring is a very useful tool. Directional boring is dependent upon ground conditions. Here is a video of the process of hydraulic directional drilling