The act of blocking one's dick from prying eyes whilst peeing in a public environment. Used by rafters or boaters when a male has to pee off the side of the boat and wants to block a direct view of his junk. Hats, a well placed hand, a map, a sandal, could all be used for the dick fence.
While Dave was taking a leak off the side of the boat, Sarah's boat floated really close by. So Dave put up a dick fence with his hat so she couldn't see how small it was.