Often referred to as DT, double terminated crystals are just that - double (meaning both) terminated (ends) are pointed. These crystals are similar metaphysically to the tower point, however instead of just having energy flow through the top point of the crystal, we have the energy flow through both top and bottom points. This energy flow through dual points allows energy to enter through one side, be transmuted through the crystal, and to flow through the other side. This flow and transference of energy is a wonderful tool for healing work, body work and works great in meditation.
DT points are also wonderful to use in crystal grids because it helps the energy of the crystals transfer between one another, amplifying the energy and allowing potent transmission.