Basic blender went bad (motor ran but spindle wasn’t rotating). I wanted to disassemble to see if it could be repaired. Three of the four screws were Phillips head. I had to cut the casing open in order to discover why I couldn’t unscrew the fourth. It was a slotted spanner.
He had to see which bit to use
That can be accomplished non-destructively.
Phone camera; $30 digital microscope; $30 Endoscope. There are just so many better ways available to look down a hole to see what’s at the bottom than to tear apart the space around it.