How do you solve the problem of locking a gate that many different parties need to open, each with a different schedule and all unaffiliated?
This lock on a ranch gate is designed for shared access by independent parties:
Seen at ranch gate outside of Lasalle, TX. Removal of any single padlock allows the central rod to retracted far enough to allow the gate to be opened. The central rod has an “L” on it (unseen) that has a diameter which allows it to pass through the hole where a padlock is attached, but only if the padlock is removed.
I’d love to share the photo, but alas, it’s all rights reserved.
I found this design puzzle and solution by way of Bruce Schneier’s blog, and reading through the comments, there are other solutions that accomplish essentially the same thing.
Given all the recent hacks and the ever-eroding username-password-as-authentication standard, there are applications of this real-world solution to software too.
Anyway, designing solutions to these types of unique problems is always a fun exercise. How would you solve this problem?