The Apollo heat flow experiment was designed to collect various measurements of heat distribution and transfer in the lunar soil using two probes inserted into holes drilled into the the moon's surface with the Apollo Lunar Surface Drill. To create holes for the placement of these probes, special bore stems were used. The bore stems were made of epoxy fiberglass containing glass and boron filaments.

The general operation involved assembling the first two bore stems, inserting them into the drill chuck, and drilling into the surface until ~1/3 of a section protruded above the surface. Using a wrench, the chuck was released and the drill was removed. A second pair of bore stems was assembled and attached to those already emplaced in the surface. The drill chuck was reset and the drill placed atop the new bore stem sections and the total bore stem assembly was drilled further until again about one third of a section remained above the surface. The procedure was repeated for a third pair of bore stems until ~15 cm remained above the surface. The drill was then removed and the Heat Flow Experiment probe was inserted as far as possible into the bore stem using the emplacement tool.

This item was not flown and was received by the Smithsonian in 1974.