I was sparring with one our blue belts again. The drill was an open guard drill. We had just learned a pass where we pass the legs and eventually get the back. The guy on the top had to pass the guard, the guy on bottom needed to sweep. I was playing on top. I took a little distance to go for my pass (which was not the one we had been shown, but a more simple one). But before I could actually do my pass my sparring partner decided to go for my leg and try to pull half guard.
The only thing was, he had no grips on me so I just side stepped and passed his open guard.
Turns out, you do need some grips when going for sweeps from the open guard.