These are antennas specifically designed to receive one channel. They are sometimes used by cable companies to pick up local stations. A large electronics supply house should be able to get them for you. The only use for one of these in a home set up is in the case of a single station located in a different direction from all the others that is difficult to pick up. Directional FM antennas are a variation of a channel cut antenna designed to pick up the FM band.
Television antennas are directional.
They should be pointed at the transmitter of the station you are trying to receive. That is the purpose of having a rotator. In case you don't know the tips of the elements need to be angled toward the transmitter. Antennas have a specification called 'gain'. This is a measure of how well the antenna will 'pull in' a signal at a specific frequency.