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These variations on the slide potentiometer theme employ conductive carbon paper (from Pasco) or conductive plastic (velostat) and a giant paper clip.
Like pots the value of this arrangements is the physical memory of the value. Note at the back how the potentiometer wiper is connected to a conductor. This is typically achieved in a conventional pot using a conductive strip next to the resistive strip. That approach is also possible. I found that the conductive tape (Laird) added friction which helps lock the slide in position.