Susan, although I did not write the script so I do not for sure the real
intent of it,  I believe the "watch your head" sign was supposed to be
a bit sarcastic and humorous.  What a better time for humor than during a
grisley maiming.    It is followed by an equally horrific but hysterical
(I found myself laughing outloud) bit of monologue by Mr. Blond.
I do not remember the exact words, but Blond held the ear to his mouth
and said to the cop something like, "Did you hear that?".  In fact the
entire absurdity of Mr. Blond's mannerisms in that sceen seem to be
entertaining.  You have an insane man about to seriously torture a cop
and all the while he is singing and dancing and being very lighthearted.
Brian Wilson,  Trenton State College