The safe. These timeless machines are some of the toughest around. How do 21st century safes keep thieves out and even protect your valuable from a raging house fire?

More than 500 super strong parts work together. The outer shell is a sandwich of ultra-tough steel and slabs of ground up rock fireproofed to 1,200 degrees. 26 hardened steel bolts clamp the door deep into the sidewalls and a lock with 1.2 million possible combinations gives easy access if you know the code.

The secret to what makes the safe so strong is the way engineers make its steel skin.

In this 300,000 square foot Utah factory that these Liberty safes begin life as 9 ton rolls of coiled up steel. It’s 5 times thicker than the steel used on car body work, and incredibly tough. Workers must wrestle this super strong steel into a precision formed box. It’s a mighty engineering challenge.

Watch this episode of the Science Channel: Machines How They Work