GadgetGuy
(Formerly Shermie)
I plan to get a pair. Not that I'm accident prone, but you never know when the blade might slip the wrong way & you end up cutting yourself!
Only the one is required.
Advice is not to use one on hand holding the knife as the knife can't be held securely. If the glove allows you to hold the knife, with no movement, chances are they'll also let the blade through in use.
They're not light in use, if you get one that's able to withstand a knife slipping. Kevlar ones are available, a bit more flexible & lighter than the one pictured.I think that they come in sets of 2 though.