What the beer is for?

A man went into the proctologist's office for his first internal exam.
The doctor told him to have a seat in the examination room and that he would be with him in just a few minutes. When the man sat down and began observing the tools, he noticed there were 3 items on a stand next to the doctor's desk.
1. A tube of K-Y jelly
2. A rubber glove
3. A beer
When the doctor finally came in, the man said "Look Doc, I'm a little confused. This is my first exam. I know what the K-Y Jelly is for, and I know
what the glove is for, but can you tell me what the BEER is for?
At that the doctor became noticeably outraged and stormed over to the door.
The doc flung the door open and yelled to his nurse, "Dammit, I said A BUTT LIGHT!"