A double bottom is two tests of the same low that both hold, forming a W. It says sellers tried twice and could not break the floor — a classic bottoming signal.
A double bottom is the mirror image: two tests of about the same low that both hold, with a bounce between them, forming a W.

Sellers pushed price down to a level, buyers absorbed it, sellers tried again, and buyers absorbed it again. The second hold is the evidence — it says the first was not luck. Whoever is buying at that price is still there and still willing.
As with the double top, the pattern confirms on the neckline — here, the peak of the bounce between the two lows. A break up through that level completes it. Volume should build on the second low and expand on the break.

One caution specific to this end of the market. A double bottom assumes the floor is demand. On a penny stock it can instead be a mechanical artifact — a conversion price in a toxic financing deal, for instance, where a holder is converting and selling at a fixed level. That produces a very convincing flat floor that breaks the moment the tranche is done. If a sub-$1 stock keeps bouncing off a precise round number, read the filings before you trust the shape.
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