These are the most commonly used on the Rocking Horse Projects. Made of birch. Standard Screwhole Buttons are used on counterusnk holes to cover screws. Buttons have a tenon to glue into 3/8" and 1/2" diameter holes. Flat bottom Domed Discs have to be glued to the surface, they do not have a tenon to glue into a hole. Flat bottom discs do come in much larger diameters than screwhole buttons.