National service

Three young men are called up for national service but must first pass
a medical. The first one enters the doctor's surgery and is asked to
strip.
"What's that?" asks the doctor.
"It's a truss" says the youth.
"And how long have you been wearing that?"
"Three years," says the youth.
The doctor goes to his clipboard and says, "ME - Medically Excused,
you can't serve in the army with that".

The youth leaves and tells his mate, who asks to borrow the truss. The
same thing happens; he comes out having been discharged.

The third youth enters, and everything's going fine until the the doctor
writes 'ME' on his form.
"What's that?" asks the youth. "Medically excused?"
"No," says the doctor, "Middle East. If you can wear a truss upside
down for three years, you can certainly serve in the middle east!".