Strategy: Signifiers

Signifiers are properties of an artifact, device or system that communicate to the user specifically where interactions should take place with the design. They are perceivable marks or sounds that tell the user what the appropriate interaction behavior should be. They are like useful signs, signals, drawings, or labels but don’t have to be as overt or intentional. For example an unintentional signifier can just be a perceived affordance that is unambiguous, like an on/off light switch.
Norman,Donald . The Design of Everyday Things (USA: Basic Books, 2013), 13-16.

To contrast the design principle of Affordances with Signifiers we can look at the example of paved roads and lots. Given a car, the relationship between the wheels and the road together demonstrate the affordance of driving across the pavement. But it is the property of painted lines on roads and in lots that indicate the possible actions a driver can take. The lines and markings are signifiers that indicate where the driving (or ceasing of driving) can take place. On paved roads they can indicate where one can turn left or right,  where you need keep driving straight, where you should avoid driving over, or where to stop the vehicle to park.

Original source image

Signifier left/right arrows on a touchscreen
Norman,Donald . The Design of Everyday Things (USA: Basic Books, 2013), 21.

Online image

The swipe signifiers on the IOS shutdown screen
https://www.igeeksblog.com/how-to-use-lockscreen-in-ios-10/

Real world image

Stripes on the pavement indicate where one can park their car. The District Parking lot, Tustin