I would like to put down 2 pieces of tongue and groove hardwood strips with their grooves facing each other. this way, I could build out from the center (I am going to put an inlay into the floor later on). anyway, does anyone know the technical term for a groove filler so that it acts like a tongue into both hardwood strips? also, where could I find this filler?

thanks.

It is called a spline. Some call it a slip tongue.

thank you.