Check-out in car rental
From the supplier’s perspective, check-out is an instance when the renter receives the rental vehicle from the supplier in the beginning of the rental period. In other words, check-out meaning is the same as pick-up or delivery.
It is important to note that this is car rental supplier specific terminology. Check-out can have a different meaning in other travel sectors. For example, in hotel business, check-out means that a visitor settles the bill and leaves the hotel.