I'm 26, I work at a desk, and until this January the most athletic thing I did was carry groceries up three flights. A coworker dragged me to the climbing gym for her birthday. I got about eight feet up the easiest wall in the building, froze, came down, and signed up for the intro class the same night. I don't entirely know why. Something about being that scared and that interested at the same time.

Here's what indoor climbing actually is, for anyone as clueless as I was.

The gym. Tall walls (ours are about 35 feet) covered in plastic holds bolted on in routes. Each route is marked with colored tape at the start and the holds you're allowed to use are the same color. Routes get changed every few weeks so it never gets boring.

Top-rope. This is how beginners climb, and how I've climbed almost all year. The rope is already hung from an anchor at the top of the wall. One end ties to your harness, it runs up through the anchor and back down to your partner, the belayer, who takes in slack as you climb. If you fall, you drop maybe a foot and hang there. It is very safe when done right and it's the "done right" part they test you on.

Lead climbing. The rope starts on the ground with you and you clip it into bolts as you go up. Falls are longer. I am not lead certified yet. That's on the list.

Bouldering. Short walls, no rope, thick pads on the floor. Good for strength and for problem solving; bad for my ankles, which I've decided I like.

The belay test. Before the gym lets you belay anyone, you take a class (two hours, $25 at mine) and then pass a test in front of a staff member. They watch you tie into your harness with a figure-eight follow-through knot, check your partner's knot and harness, load the rope into the belay device correctly, and then belay a climber all the way up and lower them down smoothly without ever taking your brake hand off the rope. Take your brake hand off, you fail. I failed the first time. I was so busy watching my partner that I let go for about half a second to adjust my glasses. The staff guy was very nice about it and I retook it the next week and passed, and I have never adjusted my glasses on belay since.

The commands. Everybody uses the same ones so there's no confusion about who's ready. Climber: "On belay?" Belayer: "Belay on." Climber: "Climbing." Belayer: "Climb on." At the top: "Take!" to get pulled tight, then "Lower!" or "Ready to lower." You say them every time, even when it's your best friend on the other end. Especially then.

Shoes. Climbing shoes are tight, have sticky rubber soles, and hurt. You rent them the first few times ($3) and then when you buy your own you buy them a size smaller than you think is reasonable, and then you sit in the car in the parking lot with them on to break them in, and then they still hurt, and then one day they don't and you can stand on a hold the size of a quarter. I bought mine in April.

Chalk. Gymnast's chalk, in a little bag on your harness. It dries your hands so you don't slip off the holds. It also gets on your clothes, your car seat, your face, and, once, my boss's office chair.

Harness. Rent ($3) until you're sure, then buy ($45 for mine). It goes around your waist and legs, and the rope ties into it through two specific loops, and you double-check the buckle every time because the belay test people made me say "buckle doubled back" out loud so many times that I now say it in my sleep.

Routes are rated so you know what you're getting into. American climbers use the Yosemite Decimal System, which is why this page lives in the Yosemite neighborhood. The general idea:

• Class 1 through 4 are walking, hiking, scrambling, and scrambling where you'd really rather have a rope. None of that is on a gym wall.
• Class 5 is technical rock climbing, with a rope. Everything in the gym is class 5, and the number after the decimal point tells you how hard.
• 5.5, 5.6, 5.7: beginner routes. Big holds, like a ladder that leans a little. Where I started.
• 5.8, 5.9: still moderate but you have to think. Smaller holds, some overhanging bits, you have to use your feet properly instead of pulling with your arms. Where I am now.
• 5.10 and up: the numbers keep going (5.11, 5.12, 5.13, and a few people in the world climb 5.14) and at 5.10 and above each number gets split into a, b, c and d, so 5.10a is easier than 5.10d. There's a 5.10a on the back wall that I have been staring at since June.

Grades are subjective and every gym is a little different, and outdoor grades are almost always harder than the same number indoors, which I found out in September. But it gives you something to chase, and I like having something to chase.

Posted on the wall by the front desk:

1. Sign the waiver. Every visit until they know your face.
2. No belaying without a belay card from this gym. They don't take other gyms' cards. Take the test.
3. Check your partner before every climb: knot, harness, belay device, carabiner locked. Say it out loud.
4. Brake hand stays on the rope. Always.
5. No climbing above the marked line on the bouldering wall without a rope.
6. Don't climb under someone. Don't walk under someone.
7. Kids under 14 must be belayed by an adult.
8. Shirts and shoes required. (There was a summer incident.)

Not posted anywhere, but learned:

• Don't give beta (advice on how to do a move) unless somebody asks. People want to figure it out.
• If somebody's on a route, it's their route until they come down. Wait.
• Brush your chalk off the holds when you're done on a boulder problem if you caked it on.
• The regulars are friendlier than they look. The guy with the beard who climbs 5.12 taught me to drop-knee for free on a Tuesday and has never mentioned it since.
• Nobody cares how hard you climb. Really. They care whether you belay well.
• Falling is normal. Falling is part of it. The first time I took a real fall on top-rope I screamed and dropped about eighteen inches and my belayer, bless her, did not laugh until I was on the ground.

From the little notebook I keep in my chalk bag. Cleaned up a bit.

The gym runs an outdoor top-rope day a few times a year for members who've never climbed on real rock. $35, a van ride to a crag about two hours out, and two instructors who set up the anchors at the top so all we had to do was tie in and climb. Eight of us went. I did not sleep the night before.

Things I learned in one day that I did not learn in eight months inside:

• Real rock does not have colored tape. There is no route. There is a wall, and you look at it, and you figure out where your hands go, and sometimes where your hands go is a crack, and a crack is not a hold, it's a puzzle. I stood at the base of the first climb for a full minute just looking.
• Outdoor grades are stiff. The first route was a 5.6. I've been climbing 5.9 in the gym. The 5.6 outside was harder than most of my gym 5.8s. Everybody in the van said the same thing. The instructors just smiled.
• Feet again. Except now the footholds are ripples in granite that I would not have noticed as footholds. Stand on them anyway. The sticky rubber does more than you think.
• It's high. Thirty-five feet in a gym is thirty-five feet with a floor and a snack bar. Sixty feet on a cliff with a valley behind you and a hawk going by at eye level is a different sixty feet. I looked down once, at the top of the second climb, and then I looked out instead, and I get it now. I get why people do this.
• The rock is warm. That's it, that's the note. It was warm and rough and it smelled like dust and pine and I put my cheek on it at the top of the last route and the instructor belaying me said "yep" like he'd seen that before.

I climbed four routes: a 5.6, a 5.7, another 5.7 and a 5.8 that I fell on twice and finished. My hands were wrecked, my legs were wrecked, I had a scrape down one shin and I slept the entire van ride back. Sunday I couldn't make a fist. Monday I signed up for the next outdoor day in October.

1. That 5.10a on the back wall. Before New Year's. I've written it on the fridge.
2. Lead class. The gym runs one in November. Falling on lead scares me more than anything about this sport and that is exactly the reason I'm taking it.
3. October outdoor day. Already paid.
4. Learn to build an anchor myself, eventually, so I don't need a gym van to go outside. That's a next-year thing. Maybe a class with a real guide service. Andrea over in Ridge does mountains and I read her whole page and got ideas.
5. Stop chalking my car.

I'll keep the log going. If you're thinking about trying this: go. Take the class. Fail the belay test if you have to and take it again. Buy the tiny shoes. It's the best thing I've done for myself in years and I was scared of it the whole time and I still am, a little, and that's fine.

— Priya