I run an Airbnb. Last month a guest sent me a message that made me sit down on the kitchen floor. It was a photo of one page from a school notebook, and five words: "His teacher asked what changed."

The boy who stopped offering his hands

Hannah and Tom stayed with us a while back with their two kids, Ollie, who was 9, and Rosie, who was 6. Ollie was very bright and knew more about sharks than I know about anything. But when something needed opening, a bag, a zipper, a bottle, he held it out and waited, and somebody took it from him and everyone kept talking.

On the second morning I put out a bowl of apples. Ollie turned one over twice and asked his mom to cut it up. She said, "Just eat it, sweetie." He tried it from the side, like a sandwich, gave up and put it back. Nine years old, and he had never eaten an apple that wasn't already in slices.

Then it rained, and Rosie found the block

I keep one small wooden block on the kitchen counter for guests. Rosie didn't put it down for two hours. Then Ollie wanted it, and there was a real fight, the kind where a parent has to separate two children and confiscate the object.

By Thursday they had a system with a kitchen timer. Nobody fought over the tablet, because there was nothing to win. They fought over the block. And Ollie, the boy who didn't offer his hands, sat at that table for four days, because his little sister could do the blue route and he couldn't, and that was intolerable.

The block was gone

When they checked out, the block was missing from the counter. I pulled the footage from the camera in the common room, which guests are told about. Hannah, at 6:50 that morning, picking it up in both hands and putting it in her bag.

I texted her. An hour later she called, already crying. "In October I sat in a little plastic chair at a parent-teacher night, and his teacher told me Ollie is the only child in his class who still can't tie his shoes. I've bought the Velcro sneakers, I cut up his fruit, I open his yogurts in the morning because we have eleven minutes to get out of the door, and I have started to wonder whether I did this." Then: "I watched him use his hands at your table for four days. On the Friday he did the blue one and stood on the chair and shouted. That's the first time in about two years I've seen him want to be good at something he can't already do."

What my husband said about kids and their hands

Mick has taught children to climb for 22 years. I asked him if kids had changed. He said, "They can't hold on." Not that they're weak, he said. It's that their hands don't know what to do. They put a hand on a hold and it just sits there, flat, like a starfish.

What I put on the counter

It's called the Boulder Block: real climbing holds on a solid wood block, 12 resin holds that unscrew and move. You climb it with your fingers only, from one hold to the next, and a Challenge Deck of 16 routes across 4 levels shows you the order. There's a hardest route they can't do yet, so it's a game with a top, and there's a sibling who might get there first.

I'm not going to pretend it's magic. It doesn't teach a child to tie a lace, and it won't fix handwriting on its own. It gives a child's hands something difficult and interesting to do, and children want to.

Up to 55% off + a free gift set with every block

The five words

I put the block on my own son's table, where he eats his cereal, and I stopped opening things for him. For two weeks he ignored it. Then he could do four routes and I couldn't, and that was the day it got interesting to him.

Last month, about nine months after the family left, Hannah sent me a photo of Ollie's school notebook, open to one page of his handwriting. I don't know what it looked like in October. She just wanted somebody to see this one. Underneath it were five words: "His teacher asked what changed."

I printed it. It's on my fridge, next to the thank-you note she left on the counter.