Final answer:
The ruler placement postulate states that you can measure the distance between two points on a ruler by aligning one point with zero on the ruler and measuring the length to the other point.
Step-by-step explanation:
The ruler placement postulate states that you can measure the distance between points A and B on a ruler by aligning point A with zero on the ruler. The distance is then equal to the length from zero to point B. For example, if point A is aligned with the zero mark on a ruler and point B is aligned with the 5 cm mark, the distance between A and B is 5 cm.