Definition - What does Trail Rod mean?
Trail rods are installed into the drill stem in order to maintain the integrity of the bore. Drill rods are necessary when the material being bored is known to be unstable and prevents complications from cave-ins after the hole has been bored or reamed.
Trenchlesspedia explains Trail Rod
Trail rods trail the drill bit or reamer and maintain the hole until a pipe can be installed. Drill rods come in various sizes to accommodate various hole sizes. Trail rods perform no cutting action and their sole purpose is to ensure the bore remains intact until a pipe can be installed.