Maca44 said:
Over the past couple of years I have been using small plastic electrical ties to secure the zipper and locks on my checked bags. After inserting the end of the strip into the locking end of the tie, it can not be reversed and has to be cut off. However, they are relatively cheap so that doens't matter. After locking the zipper sections it can be opened up slightly, well enough to insert a small nail clipper which I use to trim off the ties so no body can try and pull on them.
I use them too. But I refer to them as "Cable Ties" since they are design for tying cables together and not for passing electricity through them (they are plastic after all
).
Another recommendation is to take a photograph of the locked bag just so you have some evidence that the bag was locked (or cable-tied) at check-in. If you are paranoid, ask the check-in agent to ensure the exact weight of the bag is noted, as that action alone would have indicated whether a 4kg package had been added to someone's bag after check-in.