He is a method I have used for a long time to check traps under ice.
The wire is what is commonly called "bell wire" about 22ga.Twist together leaveing enough to pass aroung the trap jaws. Lightly
twist to form a loop around the jaws.Run the wire up above the ice.Mark your sets,frozen water pretty much all looks the same.
To check use a continuity tester or volt-ohm meter.An open circut means a trap that will need closer inspection.
This is a real time saver if you decide to try this aspect of trapping
(Edit: Title. Photos archived. -- Hal )