A Renko Bull Trap is a false breakout: the bricks rise just above a resistance level, such as a double or triple top, and then quickly reverse lower. 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. Buyers who chased the breakout are trapped, and their selling can fuel a sharp decline.