how? Decal with procedural scale

Hi, i saw this awesome video and was curious as to how this is made.

This person has put nothing in the description saying how it’s made.

I think it is made up out of 2 different decals (corner and straight) which are then placed/scaled according to the target you set, to create the rectangle shape. But I’m lost on the BP’s, anyone got a pointer in a direction? Thanks a lot!