The figure of speech being used is a pun. The deeper meaning is that the board, being an inanimate object, cannot physically become a fireman, but the pun plays on the word "drills" which can refer to both firefighting drills and woodworking tools used on a board.
this joke makes no sense to me
I apologize the joke wasn't clear for you. The joke hinges on a play on words and relies on the reader to make a connection between two different meanings of the word "drills". In this case, "drills" can refer to both firefighting drills and woodworking tools used on a board. The pun is that the board, being an inanimate object, cannot physically become a fireman, but the use of the word "drills" makes the joke work by connecting the two different contexts. If you are not familiar with these two meanings of "drills", the joke may not make sense.
The figure of speech being used is a pun, which relies on the word "drills" having a double meaning (referring to both firefighting equipment and the dental tool). The deeper meaning is that the board was hesitant to become a fireman because it was afraid of both the physical drills used in firefighting and the potential discomfort of dental drills.
The figure of speech being used in the joke is a pun. The joke is based on the double meaning of the word "drills," which can refer to the tools used by firefighters or to the act of practicing firefighting techniques. The deeper meaning is that the board, being an inanimate object, could not physically become a fireman and therefore uses the pun to create a humorous situation.
