A Renko Bear Trap is a false breakdown: the bricks fall just below a support level, such as a double or triple bottom, and then quickly reverse higher. Renko charts are built from bricks of a fixed size that ignore time and small price moves: a white brick is added when the price rises by one brick size, a black brick when it falls by one brick size. Sellers who shorted the breakdown are trapped, and their covering can fuel a strong rally.
