What is a rejection block?
At a bearish rejection block, two or more candles at a swing high leave long upper wicks: buyers pushed price up, sellers drove it straight back down. The zone runs from the highest body (open or close) to the highest wick.
When price returns to that area, traders look to sell at the body level, with the stop above the wicks. A bullish rejection block forms at a swing low with long lower wicks.