To be able to use information from other sources for locating points, you'll need to know what the "cun" is.
The "cun" is the standard unit of measurement for the body used in acupuncture. As everyone's body has different dimensions, it is defined according to the person whose body is to be treated.
1 cun = width of the thumb, in the middle, at the crease
3 cun = combined breadth of the 4 fingers, at the level of the pinky finger's first joint above the palm of the hand
12 cun = the distance from the elbow crease to the wrist crease.