Plastic surgery textbooks divide up faces into thirds and fifths and speak of the proper angle and projection of the nasal tip.

She said that the device must be placed at the proper angle or it won't work.

This action measured the wind speed, and moved the sights to the proper angle to account for it, eliminating the need for separate calculations.

When closed, the striking surface was positioned so that the flint would strike at the proper angle to generate a spark.

Then, using both values, they would look up the proper angle for the sights, the so-called range angle, and set the sites to that angle.