I’ve done this several times and pulled the chicken for sandwhiches and the like. However, I’ve had two conversations this week with folks who didn’t necessarily get what I was talking about. So here’s a shot of a “spatchcock” or butterflied chicken.
To do this, just cut down each side of the backbone/spine of a whole chicken and remove it. Place your fingers in each side of the incision, press inward on the breast bone with your thumbs, pull each side apart apart at the incision that you’ve made, and the breast bone will crack open till the bird lies flat. I grill these at ~325 degrees or so for ~1 hour & 15 mins (or until they’re done).
If you haven’t tried this, you should. It’s pretty darned tasty.

Cheers,
Braddog