A clothes shop was running a promotion giving away free jeans.
In order to get the free jeans you had to try a pair on, then, while still wearing the jeans
you had to put your right hand in the left pocket
and your left hand in the right pocket
and reach right to the bottom of the pockets at the same time.
Many people tried but were unable to achieve the feat until,
One chap walked in and walked out a few minutes later with his free jeans.
How did he do it?
He tried the jeans on inside-out.
The left pocket was then on his right side and the right pocket was then on his left side.
Alternate answer: He tried the jeans on backwards.