Tolerance stacks

Tolerance stacks are like building with lots of different sized blocks. They help when someone wants to make something fit perfectly. Let's say you have a person who is 5 ft tall and someone who is 6 ft tall, and you have a doorway that needs to have an exact size of 5 ft and 6 inches. If you had 5 blocks of different sizes (one is 5ft, one is 6ft and 3 others in between) and put them all together, you would be able to perfectly fit the doorway! That's what tolerance stacks do – they help put together different things to fit perfectly.