Belt and braces
Definition 1 of 1
Pro Tip 1/3Redundancy Intended
Implying extra precautions were taken even though they might seem unnecessary. 
Although the alarm was set, he followed a belt and braces method by also having a guard dog.
Pro Tip 2/3British Origin
It's a British expression, so be aware it may not be understood globally. 
Our UK team prefers a belt and braces policy to avoid any risks.
Pro Tip 3/3Primarily Formal
Better suited for formal or business contexts where precision is valued. 
The engineer recommended a belt and braces check of the system before launch.