A straight or curved strip of wood, metal, etc., with a smooth edge, used for guiding a pen or pencil in drawing lines. Cf. Rule, n., 7 (a)<-- usu. marked with graduations so that it can be used to measure distances -->.

A horizontal or vertical bar marked with measurements such as inches that displays, respectively, at the top or side of the Slide pane.

measuring stick consisting of a strip of wood or metal or plastic with a straight edge that is used for drawing straight lines and measuring lengths

an instrument used in geometry and technical drawing to measure short distances and/or to rule straight lines

the planet that rules a given sign or house

the planet ruling the rising sign (Ascendant) is said to be the Ruler of the chart. Thus if you have Cancer (or Gemini) rising, the Moon (or Mercury) is the ruler of your chart.

A planet is said to rule a house when it rules the sign on the cusp of that house.

Each Sign of the Zodiac and each of the 12 Houses are associated with a specific Planetary energy, and is said to be ruled by that Planet. The Planet that rules the sign on the Ascendant is called the Chart Ruler.