When someone "holds in" their bowel movements for at least three days. They then have someone lie down on the floor face up the person lying down is called the "trailer". Then the the person that hasn't had a bowel movement procceeds to give him/herself an enema using motor oil. After the extreme feeling of I-have-to-shit happens, the trailer then opens their mouth and the person jumps over them and tries to shit in their mouth.

When you eat dirt for the first time and leave your family to build a shack in the woods