"Sometimes we want a detail in one area, or paint an object esculpted … with details. How do I know where everything will be the object? Textures are numbered for this. The place or object in the face we want to know where to paint. Guided by the grid of numbers and letters and we can find guidance in our canvas photoshop where to draw / paint. As in the SL templates, they must have in SL as in RL."
SileneChristen’s Blog - Second Life Tutorials