Thats a good Idea Ilplumber.
I had this happen to me a month ago. I was called in for a toilet leak at the base. Turns out it was the supply flex on the 3/8" side. I think "hmmn I'll just tighten it a bit and see what happens"...
Well, the stop broke in half and I hardly put any pressure on it. Luckily the HO was standing there and new how to shut his water off. I palmed it to minimize the flood.
I keep channel locks in my back pocket... Wish I would have thought about pinching it off...
Anyways, I now take a sharkbite cap with me whan I decide to play with angle stops

I'm scarred fro life!