Every slot canyon tells you what it's going to do, if you know where to look. Here's how we read one from the rim, before a rope comes out of the bag.

Watch the water line

Sandstone holds a high-water mark like a bathtub ring. If the stains are dark and fresh, the last flash flood wasn't long ago — and the pools below are probably full and cold.

Check the walls, not the map

Maps flatten a slot. What matters is the squeeze: if the walls are polished and smooth where you'd stem, the water runs fast there. Polished rock means wet feet, cold hands, and more friction in the rig.

Find the last exit

Before you drop the first rappel, know the last point you can walk out. After that, it's rope to the end. We mark it on every route — in red, so you can't skim past it.