Here's the background, as reported in PoopReport's Movie Poop-Scene Archive [2]:
Entry #2: The previous poster forgot to mention that after the smart-ass's "three seashells" remark, Stallone gets in front of the credit fine machine and starts cussing, producing several fine credits because of violation of the verbal morality act. He uses these pieces of paper to relieve himself of trying to figure out the three seashells. And here's a screenshot of the apparatus in question: Despite the best efforts [3] of the members of this site, we've found no reasonable answer to this question. But in an interview on Ain't It Cool News [4] (question 9), Stallone himself shed some light on the issue:
A: OK, this may be bordering on the grotesque, but the way it was explained to me by the writer is you hold two seashells like chopsticks, pull gently and scrape what's left with the third. You asked for it... Be careful what you ask for, sorry. There you hav-- hmm. I'm thinking about it. I'm using my imagination. I'm pantomiming it here in my desk chair. No... nope. I still don't get it.
And I'm not alone. Ignoring the bizarre physical contortions this would require, and the pain such scraping would engender, there are these concerns as outlined by an AICN commentator: "Aside from saving paper, what's the futuristic benefit? Who washes the seashells? If you don't get a perfect swipe the first time, what the hell do you do in your stall with feces-covered seashells?"
Indeed. The future is still a mystery. According to IMDB.com [5], story credit for Demolition Man go to Peter M. Lenkov and Robert Reneau, with Daniel Waters sharing screenplay credit. Some intrepid PoopReporter needs to track one of them down and ask them directly.
Entry #1: Sylvester Stallone plays a cop who is cryogenically frozen for some crime, then thawed out in the future to track down his nemesis, who has escaped. At one point Stallone goes for a crap and finds that they don't use toilet paper in the future. One smart-ass comments, "Maybe we should tell him what the seashells are for."
Q: For the love of all that is good and Holy. How do you use the 3 seashells?!