I find it surprising you work around machines and do not know about using a solid object to bring sound from one point to your ear as a diagnostic technique.
I felt my response was rather restrained. My posting a heartfelt rant might end up with me being a former member of this or any other forum.
I think it was someone with an electrical problem to cause me to decide against giving advice on electrical problems. It seemed the person may have been headed towards an electrocution of their self.
Now I get the block of wood thing at the end but not the hole.
The hole is a mortise to hold the dowel, possibly the quickest way to attach a piece to a dowel. It creates a platform for the ear and a wider area for the sound to resonate. Kind of like the top of a screwdriver handle on which to rest one 's ear. Placing the dowel directly in one's ear can be uncomfortable.
jtk
"A pessimist sees the difficulty in every opportunity; an optimist sees the opportunity in every difficulty."
- Sir Winston Churchill (1874-1965)