Lucus makes a clenched fist and taps the palm of his other hand on top of it. It's one of his favourite signs: more.
Makaton signs have "completely changed" how Lucus, who has Down's syndrome, communicates, according to his 13-year-old sister Isabella.
She has now launched a petition calling for the communication tool to be taught in all schools across Wales.
The Welsh Government said all schools "can choose to teach and use Makaton".
Makaton uses signs and symbols to help people who find speaking difficult.
YouTuber Isabella, from Bridgend, has also taken to social media to share Makaton signs and tips with others on her Youtube channel Isabella Signs.
She said not only has it made an "amazing" difference to Lucus' speech and communication, but he has also become less stressed.
"Before, we wouldn't understand simple things he meant, he would get frustrated and shout," she said.
"Now some of his friends can sign 'good morning', or simple things back to him.
"It would be heart-breaking for me if no-one could understand him."
Makaton is different to British Sign Language (BSL) because it only has individual signs for words, whereas BSL has its own grammar and word order, and is a recognised language.
Isabella wrote in her e-petition that Makaton was a "fundamental right" for children "in order to break down barriers, misconceptions and achieve true inclusion within Wales".
It has racked up more than 500 signatures from people across the UK.
She said it was not easy to learn, as the signs are not all in one place online, but she hoped in time "it will be more accessible when more people are aware".
Jade Kilduffy, from Heywood, Greater Manchester, also uses Makaton to communicate with her four-year-old brother Christian, and said the petition was "fantastic".
Christian, who has cerebral palsy, used get "frustrated" trying to communicate but now he is able to get his feelings across, said the 18-year-old.
"I don't want him to have nobody to talk to. I want him to talk to everyone and not just us," she said.
"He has started speaking and he is using Makaton more, which has really helped him develop. It has massively changed his life," she added.
Ms Kilduffy said she wanted to pursue a career as a special educational needs teacher and enjoyed using YouTube to teach a sign a day to her brother on "Sign along with us".
The Makaton Charity said there were between 100,000 and 150,000 people with a learning or communication difficulty who regularly use their Makaton Language programme.
Today’s sign is THUNDER, as it’s just been thundering here. I thought Christian might be scared but he thought the sound was funny 😁 I think his signing is coming on so well , really proud of him x @ZebedeeMan pic.twitter.com/1Tqmeftiez— sign along with us (@signalongwithus) April 25, 2019
"Languages, Literacy and Communication is one of six areas of learning and experience in the new curriculum for Wales," a Welsh Government spokesperson said.
"Where appropriate, schools can introduce British Sign Language as their international language."