I don't understand what this is. Do you have pictures or a video showing application?

This is a component of the Domino XL knock-down connector system. Below is a link to the video and a full listing of the connectors which are available for the Domino XL and DF 500.https://www.youtube.com/watch?list=PLFGIE_jCN0y4erQBEt8vV3qkgVs1YzH2fhttps://www.festoolproducts.com/accessories/domino-joiners/domino-rta-connector-system.html