The original is made of aluminum, but it was too expensive for me to connect small wooden slats. Since my construction doesn't have to withstand much, I printed it out of PLA and PETG.
Link to the original metal : https://www.sherpa-connector.com/en/products/assemblyseries/3462_230_shop_SHERPA-WTS-1.aspx?LNG=en
The author marked this model as their own original creation.