This act was not one I took part in, although I was the victim of on many occasions;
The object of Sneaky Bollock is to bare one's teste through the zip at the front of your trousers. Then, sitting in a suitable gaping position, you would call people over to "check your work" or something. They would then be horrified at the small hairy lump protruding from the loins.
For extra points, you may consider the following:
-Get a teacher with a Sneaky Bollock;
-Go the whole hog and flop your entire meatsack out;
-Draw a smiley face, or write a message to the victim on your scrotum;
-Walk around the classroom with yourself on show;
-See how long you can stand in a conversation with someone without them noticing.
In the last days of the school year, Sneaky Bollock was rife in our ranks, and the words "Hey, can you just check this for me?" filled our hearts with unmitigated fear.