This is the block that with the inside screw holes will be attached to the arch, and with the outside holes to the wall. This will be clearer in a later photo when the assembly is complete.
I cut some plugs out of a same color scrap piece of wood, to cover the screw hole after the
block is attached to the wall. This will cover the hole, and make the screw almost invisible.
The plug will be glued in place, cut off and sanded.