Reusing Zip Ties

I have a friend who is really into zip ties, like he uses them like a book strap to hold his items together, and mends things with them. He has special reusable ones, which made me think there must be a way to reuse zip ties (this was one of my pet projects when I was little, and I never succeeded) and it turns out all you do is push the locking tab out of the way of the teeth. And then the next day at work I had to unpack a pallet of dollies and was able to salvage all but one super industrial tie (it was on too tight). To avoid hurting myself I unpacked the pallet really, really slowly since each unit of dollies was unbalanced and heavy.