Jumps

They don't have to be big to be clever as a good course designer will put a jump in such a place that experienced confident riders will be able to clear an obstacle by using them. Where as an inexperienced rider may be put off by the mere sight of a jump in an awkward position and then be forced to go round losing speed.

This is known as using the "chicken run", in some cases the chicken run might be not only the safest option but some times also the quickest.