A mason's trick

Masons have several "tricks" up their sleeves that they will use in the course of doing work.

One of these tricks is pretty sneaky and rather clever.  It's about insuring that they get paid for their work.

One of the most common jobs a mason is hired for is to build chimneys.  Anyone who has ever worked in construction -as a contractor- probably has their own tales about not being paid by the homeowner, or the main contractor, if you work as a subcontractor.  Here's a trick masons use to make sure they get paid when they build a chimney.

Toward the top of the chimney, a piece of plate glass is placed in the mortar, between bricks.  The plate glass is located so that it obstructs the air flow in the chimney.  If someone tries to start a fire, the chimney won't draw at all, and the house will fill with smoke.  If the homeowner looks up the chimney, they will see the sky, and will wonder "why doesn't this chimney work?"  Now if they haven't paid the mason, he or she can say:  "Pay me and I'll fix it."  After being paid, the mason then breaks the glass and the chimney works fine.

Just a method to ensure payment.   But if you upset the mason while they're working, you might end up with this: