Horizontal Support

Horizontal support is a constant price. The market turned up from it before, and the line does not slope. Prior lows, the bottom of a range, and a breakout price that is being retested are the usual sources.

A horizontal line through reaction lows. It should be obvious on a clean chart. If you need a slope to touch the lows, you want a support trendline instead.

A hold of horizontal support is easier to test than a sloping line, because the price does not change while you wait. Buyers use a close back above the line after a test, with risk under the zone.

A close under horizontal support is unambiguous in a way a trendline break is not. Everyone can see the same price. That clarity is why the first break is often a sweep of stops.

Picking the exact low tick as the only price that counts, and ignoring a cluster a few ticks above it.

Flat levels from far away, on a price that has since split or rallied for years, may be irrelevant. Prefer levels the current campaign has actually traded.