Walk-In
A walk-in is renting without having booked ahead: you arrive at the desk and ask for a car there and then. If something is available you can drive away, but you take whatever the branch has and pay the rate of the day.
The downside is usually price and choice. Walk-in rates tend to be higher than booking online in advance, the cheaper categories may be gone, and at busy times — peak season, a flight wave, a holiday weekend — there may be no car at all.
It does have its place. Plans change, trips get extended, and sometimes you simply need a car you did not foresee. In a quiet period a walk-in can work fine, even occasionally turning up a last-minute deal on an idle vehicle.
As a rule, book ahead whenever you can — it locks in a better price, guarantees the category you want, and turns the counter visit into a quick collection rather than a gamble on availability.
Related terms
Voucher
The confirmation document proving your prepaid booking, presented at the desk to collect the car.
Peak Season
The busy travel periods when demand and rental prices rise and cars sell out earliest.
No-Show
Failing to collect a booked car without cancelling — usually forfeiting all or most of what you paid.