Junk Yard · Sharing with your other devices
What does the Sharing switch in the Junk Yard header do?
Short answer: Sharing is the master switch for sending your copies to connected Bridge devices. Off means nothing you copy leaves this Mac, regardless of per-device settings. It's independent of Capturing.
Sharing is the master switch for sending what you copy to your connected Bridge devices. Turn it off — it then reads "Share off" — and nothing you copy leaves this Mac, whatever each device's own Share my clipboard switch says.
It's independent of Capturing: you can keep a private local Junk Yard without sharing, share without saving locally, do both, or neither. Sharing also only happens while a device you share with is actually connected.