A small piece of blue cardboard

When I was small my parents stole my laughter.  ‘Too loud’ they said as they locked it in a box on a high shelf.  For years I would silently shake instead,  I started to forget how chuckling and cackling felt.  Later, I grew and reached the treasure chest while the old folks watched soaps.  Looking inside, there was a Knock Knock joke printed on a small piece of blue cardboard.  It wasn’t funny.