What is a rotary build?

I was Koush IRC channel and someone mentioned about "new build with latest code + new frg83 blobs + rotary is starting now". What is a rotary build?

rotary lock instead of the normal sliders like old school

About time... I hope he means a rotary dialer though, that would be groundbreaking... haha

If that comes out in the next nightly, I will for sure be flashing them again. I have missed the rotary for so long.