Double Top / Bottom
Price tests the same level twice and turns - strong reversal signal.
Double top: price hits resistance, pulls back, hits again, fails - buyers exhausted. Short signal triggers when the low between peaks breaks. Target = peak-to-low distance subtracted from the low. Double bottom is the mirror. ~70% reliable, but only after the key level breaks.
In plain words
Price tries the same ceiling twice and turns back twice - buyers out of fuel. Mirror: two equal lows = bullish reversal signal.
Example
ETH 2021: double top 4.4k (Nov) and 4.85k (Nov), neckline break 3.9k = bear down to 880 USD.
Also known as: M-top, W-bottom