L: Lift hill segment - Activated by pressing "Ctrl and 4", or selecting segment; lift.
This is used to carry the train to its tallest part (in most cases), giving the train enough energy to complete the course.
Lift hills should be made into at least three pieces. One leading into the straight section, one straight section (you do this by highlighting the segment and pressing "I") and finally a section leading out of the lift hill and into the drop/element.
Hope this helps.