A rhombic antenna can be made of two obtuse-angle V antennas that are placed side by side, erected in a horizontal plane, and terminated so the antenna is nonresonant and unidirectional. The antenna is placed end to end and terminated by a noninductive resistor to produce a uni-directional pattern.
http://www.tpub.com/neets/book10/42o.htm
Rhombics are high gain directive wire antennas. A rhombic is shaped like a diamond, if you're looking down on it. I.e., there are 4 'legs', 2 end 'points', and 2 side 'corners'. This one was designed for 10 meters and 6 meters, but it's proven useful all the way down to 30 meters. This particular rhombic is 120' long, 70' on a leg, 25' high, and it's a "terminated" rhombic.
http://www.fullwave.com/fsj/rhom1.htm