If you don’t want to wait in a potentially long security line at the airport, you have a couple of options you can get for “free” by having the right credit card—going in the (hopefully) shorter TSA PreCheck line or going through the CLEAR line. (I say “free” because you did pay an annual fee for the credit card, even if the credit you get from the card covers the cost of PreCheck or CLEAR.) Sometimes there’s also a separate security line for premium-cabin passengers, depending on where you are and what cabin you’re flying in, but those are harder to come by, of course.

But what do you do if you don’t have TSA PreCheck or CLEAR? For example, what if you’re in another country flying home? I’ve legit overheard people talking in the terminal at Heathrow asking about where to find TSA PreCheck because sometimes people assume it’s everywhere, but alas, it’s just in the US. PreCheck won’t save you from a long line at CDG, PVG, or GIG. (Paris – Charles de Gaulle, Shanghai Pudong, or Rio de Janeiro, if you were wondering.)

So if you’d like to avoid interminable security lines at airports abroad or if you just don’t want to risk the TSA PreCheck or CLEAR lines in US airports being just as long as the regular security lines, you should know about this alternative: Reserve by CLEAR.

Each airport calls it something different—at SEA it’s called Spot Saver, at LHR it’s Heathrow Timeslot—but it’s all basically the same thing that’s run by the same people who run CLEAR. And this option is free.

How it works

If you’re flying out of one of the airports that has Reserve by CLEAR and need to go through security, go to the airport’s website at least a week before your flight and find out what they call their local version of this program. There may be an app you can download, or you could potentially just make your appointment online.

Check to see how many days in advance they allow you to book security appointments slots. Seattle allows it five days in advance of a flight, and last I checked, Heathrow allows it four days ahead. I just poked around looking at what other airports do and discovered that LAX lets you book a whole month in advance, which is awesome and unusual. The slots do fill up, so don’t wait until the last minute to book one.

When it’s time for you to book your appointment slot, it’ll ask you what day you’re flying, where you’re flying to, what airline you’re on, and then what flight you’re on. Based on that information, it’ll let you pick from a range of appointment times usually in 15-minute intervals. You can book a slot for a group of up to ten people traveling together.

Once you’ve picked your appointment time, they’ll email you a confirmation and include a QR code, which is what you’ll show the security agent at the designated security entrance when you get to the airport.

Once you show your QR code from the email, you’ll be escorted up to the front of the security line, usually right by the x-ray belts you load all your stuff onto before you walk through the metal detectors. If you’re in the US and you have TSA PreCheck, you can mention that to the security agent and they’ll usually give you some kind of pass to hold to indicate to the agents working the security machines that you don’t need to take your shoes off or unload electronics. (In Seattle, it’s been a laminated piece of paper that kind of reminds me of an elementary-school hall pass.)

You’ll then go through the security machines like you usually would.

How to time your appointment

• The choices for appointment times usually start around 6 hours before your departure time for international flights or 3 hours before your departure time for domestic flights and go up until about 90 minutes before departure.

• They give you a grace period of about 15 minutes on either side of your appointment time in case you’re running a little ahead or a little late, but if you miss the appointment by much more than that, it’s up to the individual security agent whether they’ll let you in or whether you’ll have to go through another security line and forfeit your spot. (Once we were 30 minutes late to ours at SEA and we were turned away and had to go through the CLEAR line instead.)

• I’d advise picking an appointment slot that’s realistic but also maybe make it one 15-minute interval later than you’d like, just in case you’re running late. My reasoning is that if you’re running early, either they’ll let you in early or they won’t let you in early and then you either wait around for your actual appointment slot or you just risk going through the regular security line. But it wouldn’t matter much because you’re so early; you’re not risking missing your flight. But if you’re actually running later than you planned, that’s when you really, really don’t want to risk being turned away from your appointment slot, right? And that’s when having a scheduled appointment will save the day. So aim for whatever you think a reasonable time slot would be, but then move forward one slot in case you’re late. That’s my best advice.

Be aware of restrictions

I’ve had a friend tell me that when she tried to use Spot Saver at SEA, the security agent told her that passengers who actually do have TSA PreCheck or CLEAR aren’t allowed to use it. But my family has used it several times, and we have both PreCheck and CLEAR, so . . . who knows. I think at least at Seattle you have to be able to use it because they actually give you a pass to not have to take your shoes off if you have PreCheck, and they wouldn’t do that if you weren’t allowed to use Spot Saver in the first place. But I have seen some airports’ pages indicate that you’re not supposed to use it if you have PreCheck or CLEAR, so be warned that that may be something to look out for.

Also, don’t try to game the system if you see that all the slots allotted for your flight are full but there are other slots available for other flights. Your appointment information has to match what’s on your boarding pass.

Creative-thinking exercise

Now, if you’re already trying to figure out what you could do if all your time slots are full, but you could get to the airport earlier and get an appointment then, I’ll mention that Southwest tickets are refundable as long as you cancel tickets at least 10 minutes before departure, so if you can get from the Southwest terminal to your actual terminal airside (without having to go through security a second time), you could (theoretically) book a Southwest ticket for earlier in the day, make a security appointment based on that flight information, go through security, cancel the Southwest flight before it leaves so you get your points or money back, and then just hang out in the airport lounge for longer until your actual flight. (That earlier Southwest ticket could also get you into the lounge more than the typical 3 hours ahead of time most lounges allow.) I’m not sure if that would ever make sense, but I’m just thinking about options. You do what you need to do.

Where can I book these security appointments?

These airports offer security appointment slots:

In the US: JFK, LAX, MCO, DFW*, IAH, DEN, PHX, EWR, MSP, SEA

In Canada: YYC, YUL, YYZ, YVR, YHZ, YEG

In Europe: AMS, LTN, LHR, BER, HAJ*, FCO, FRA

(* I don’t think the security-appointment systems at DFW or HAJ are actually operated by CLEAR like all the others are, but they seem to work similarly. The weird part about DFW is that they seem to be offering appointments using SignUp Genius, which just makes me laugh because that’s what you use to figure out what week you’re in charge of bringing soccer team snacks or who’s bringing which item to a class party. I don’t think of airport security when I think of SignUp Genius! But maybe now I will, I guess?)