I recently taught Vinny the difference between slotted
screw heads. Then, when he and his screwdriver-obsessed brain encountered the buttons on Mama and Daddy's shirts, he declared that Mama's shirt
is slotted, and Daddy's
* The picture is a little overexposed, but the thread attaching the button to the shirt is making an X shape.
Actual screw head photos from McLendon's Hardware.