What does 1:12 mean, exactly? According to wheelchairramp.org, slope is the right-angle relationship of vertical height (rise) to horizontal length or projection (run). It is usually expressed as a ratio of these two measurements, with the rise figure frequently set at a unit of one. For example, a slope of 1:12 means that as each dimension unit of height changes, the other right-angle side projects out 12 units, which together result in a certain angle for the inclined, third side of the triangle. It's important to point out that the larger the run figure in a slope ratio, the gentler the angle for the inclined surface will be - a 1:16 slope, for example, is not as steep as a 1:12 slope. This fact is a source of initial confusion for many people, who conceptualize that a bigger number must mean a steeper slope.