The squirrels figured out how to open the bird suet feeder.
They chewed off the bread bag twisty-ties I used to secure it.
They somehow managed to remove the paperclip I fastened there yesterday.
If they foil me on this safety device, I will set up a video camera to catch them in the act.
Note: I bought that combination lock at Staples. You push the dial between the four directions: north-south-east-west, and you can set your own code. It helps if you have a sentence to remember your combination: Ethel Works Whenever She Wants New Stuff. The combination can be as long as you want. Bill needed four locks for his gear, didn’t want to have keys that would get lost, and didn’t want to have to remember different combinations. These locks helped greatly.
Reit This Way 
Those are some lucky birds to have you keeping their food supply safe. I think you have a winner idea here, but if the squirrels get past that, yes, I want to see!
I live in HI now and at least I don't think they have any squirrels . . . in MD they were aplenty and very apt at making a mess and leaving nothing for the birds. Dern critters!
I don't know, the squirrels around here seem to be really smart. I sure hope that lock keeps them at bay 😉