What is the half circle cut out on the spine for?

[ponq]

 

[gosuto]

Kershaw said at shotshow when it was a new model that there's no reason for it. It's just an aesthetic design choice

 

[zombieassassin]

Striking a firesteel? Maybe?

 

[TravisH]

Striking a firesteel? Maybe?

Yeah, typically a bushcraft feature found on fixed blades.

In this case, to go along with the combo edge, Kershaw's way of saying - "yeah, we be bad".