A Beer?

It was my first time visiting Dr. Putz for a colonoscopy.
 
I went into his office for my very first rectal exam.
 
His new blond nurse, Ethel, took me to an examining room.
 
She told me to get undressed and have a seat until the doctor could see me. She said that he would only be a few minutes. After putting on the gown that she gave me I sat down.
 
While waiting I observed there were three items on a stand next to the exam table:
A Tube of K-Y jelly,
A rubber glove
And a beer.
 
 
When Dr. Putz finally came in I said, "Look Doc, I'm a little confused. This is my first exam. I know what the K-Y is for, and I know what the glove is for, but can you tell me what the BEER is for?"
 
At that, Doctor Putz became noticeably outraged and stormed over to the door. He flung the door open and yelled to his new blonde nurse: 
 
"Damn it, Ethel! I said a BUTT light."

Courtesy of BabaMail