The position. The rise might be deceiving in regard to the real fish's position. The fisherman will only see the breaking surface. The rise will not reveal whether the trout drifted one meter or five meters to grab the insect. Whether it came from the right, the left, from upstream or downstream. Rises may even be misleading about the real number of trout, in fact a trout may take insects by moving several meters away within few seconds, to then come back to rise on position number one.