The Fun Lock is the easiest of four lock puzzles from Puzzlocks. Handmade these are adapted from standard padlocks so have the unassuming appearance of your regular padlock (aside from the name of the puzzle etched on the front...). These are made by Boaz Feldman who has a couple of other designs of his own, the B-Lock and B-Lock II.
The premise is easy, open the lock and it comes with a single key attached via a loop. It is always the first thing you have to try despite knowing full well it won't work but put the key in the lock and try it, no luck! If you've had a go at some lock puzzles before you will probably arrive at the solution fairly quickly but some may find it takes longer than it should!
Without wanting to give away the solution this is not on the same level as the other locks from Puzzlocks. Having said that it is a good introduction to lock puzzles and isn't so challenging it will have you throwing it at the wall or putting it in a drawer and forgetting about it. A nice piece for collectors as well who want to have the set from Puzzlocks. If you'd like to pick up a Fun Lock you can find those here.