I'll Tap Your Bonnet 

A term used widely by South Africans to exclaim dismay at another road user or offensive person also threatening with violence to follow. Originated from the action of slamming your hands on a car’s hood (bonnet) to get the attention of the driver.

If you continue moving forward and hit my bike, I'll tap your bonnet.

I'll Tap Your Bonnet by BigPapaJaco November 17, 2010