I used to work at a shoe recycling plant.

This joke springs from a delightful bit of linguistic trickery, hinging on a classic homophone pun. The humor is entirely in the clever switch between "sole" – referring to the bottom part of a shoe, something you'd encounter endlessly at a shoe recycling facility – and "soul," as in one's spirit or inner self.

The setup cleverly establishes a mundane, slightly unusual job scenario. The punchline then expertly plays on the common idiom "soul destroying," a phrase used to describe work that is incredibly tedious, monotonous, or utterly demoralizing, effectively draining an individual's spirit. By applying this literal interpretation to a job literally handling shoe soles, the joke finds its comedic footing, turning a common complaint about work into a surprisingly literal, shoe-centric predicament. It’s a great example of how a simple sound-alike can transform a mundane job into a moment of clever, groan-worthy humor.