This sexy piece of hardware is a quick-release pin. The ball end of the pin locks into a socket within the latch bolt.
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To release it, you press the spring-loaded button in the head of the latch bolt.
Originally designed for automotive applications, you can use them anywhere you’ve got a panel that you’d like to quickly remove.
Tool Zone sells four-packs for $20. They’re availalbe in six colors.
I believe that these were originally invented by Texas-based Quik-Latch.
Source: core77