Horizontal Hole Openers, also known as HDD Reamers, are used to enlarge the pilot hole in Horizontal Directional Drilling(HDD) HDD is used when trenching and excavating is not practical. This drilling technology allows for a steerable trenchless way to drill underground.  There are three stages: 1>the first stage is to drill a small diameter pilot hole. 2>The second stage is enlarge the hole with a larger diameter cutting tool called an HDD Reamer,Rock Reamer or Hole Opener. 3>The third stage is inserting the casing pipe or other product into the enlarged hole