Three shells?!
Question: How do the three shells from the movie demolition man work?
Answers: How do the three shells from the movie demolition man work?
They never explain it, perhaps it's supposed to be a joke. It's left open for you to use your own imagination. I thought it was genious for them not to explain it. One interpretation, however, is that one or more were used as a replacement for toilet paper. During filming, Stallone actually asked the writer about it and he got this answer:
"...as it was explained to me by the writer, you hold two seashells like chopsticks, pull gently and scrape what’s left with the third". Gross!