A lot of things come with plastic cable ties on them. Cable ties are very durable and I can only take them off with scissors. Because they're so durable, I want to be able to use them for other things. How can I undo a plastic cable tie so that it is still usable?
In case you don't know what a cable tie is:
Note: Some people call them zip ties
As you can see it the images you've provided, there is usually a small tab that slots into the grooves of the zip tie in order to stop the cable undoing, some of the smaller ones used with electronics can relatively easily be undone by simply pulling either side hard, however, for more heavy duty ones, this is near impossible to do so you'll need to do something else.
If you get something small and pointy (a pin or needle but other small objects will work) and put into the block with this tab and try to pull it down with the object you are using and then it should undo very easily!
It won't damage the zip tie and it will still be useable and once you've had a couple of goes at it, it'll be very easy for you to do. Some more expensive zip ties have a small button like thing on the block which will undo the zip tie by moving this tab out of the way, so if you use them a lot you could look into investing in something like this.
Here is a link to a similar method to the one I have mentioned previously with a slight variation.
Another option, only available if you can tighten it a little more, is to insert a bit of plastic or paper from the other side and let it slide under the ratchet to hold it up, ready for you to pull the rest out again.
