What's the purpose of the parking brake "cap" button?

[roscoefj60]

Sorry for the novice question but I haven't quite figured out the purpose of the Cap or button on top of the middle of the parking brake.

Can someone explain what this is for, or how's it's different from most other parking brakes that don't have this feature?

 

[onemanarmy]

It threads onto the end of the cable for adjustment

 

[roscoefj60]

It threads onto the end of the cable for adjustment

Is it used in the normal daily function of the parking brake?

Or only needed very rarely when an adjustment is needed? (When/why would that be?)