The are carved from solid blocks of wood. So no you can’t unscrew them. I’m not certain the gap size but will measure. I kind of just eyeball it as after doing several the eyes just know what works. I believe it’s usually right at or under 1/8 of an inch. Thanks for the follow as well. Hope to be producing some purple heart soon as well as Wenge with the maple sides. Should make some stunning contrasts.