Friction on Inclines

“A box is sliding down a ramp. In what direction does friction act on the box, and how does this affect the box's speed? You are pushing a heavy crate *up* a ramp. In what direction does friction act on the crate, and how does this affect the amount of force you need to apply? A toy car is placed on a ramp. Friction prevents it from sliding down. Explain how friction is acting on the car in this situation.”