Re: Why are there holes in crackers?

The little holes you see in crackers are called "docking" holes.  They are 
put into the dough before baking to prevent the dough from bubbling.

There are a couple of ways to see and understand what I'm talking about.
1.  Take a cracker and carefully break it across its entire width.  Look 
at the cracker from the broken side.  You will see where the holes are at 
because the dough is compressed and doesn't have any layers.  You will see 
the same look on the edge where the dough was "crimped" together when it 
was cut from the dough sheet.  The space between the holes will have 
layers of dough with air holes in between.  If a hole wasn't punched into 
the dough, that air hole between layers would have gotten bigger.  If no 
holes were punched you can imaging what the baked product would look like, 
a big ball with nothing but air in the middle.
2.  Have you ever had a pizza with a big "blister" on it?  The blister 
will be a big puffy area.  Normally it will be somewhat burned.  All the 
cheese and toppings normally slide off of it.  If you see this, try 
tearing the pizza across the blisher.  Inside you will find...nothing but 
a big hole!  

This happens because air gets caught in the dough.  If there are no holes, 
there is no place for the air to go.  As the pizza or cracker starts to 
heat up the air expands and gets bigger.  If there is now way for the air 
to escape it will just keep getting bigger and bigger till the dough 
breaks or is set (hardened during cooking).