The stuff they tend to make stab proof material out of - kevlar, forms of dyneema - all pretty much works on the basis of very very tightly woven super strong fibres. For example derivatives of Dyneema are used for modern archery strings - you can get breaking strengths of 60 - 200Lb per strand if even that low, realistically. This means that a bullet cannot necessarily penetrate until it unravels these fibres and parts the weave, same with a knife. This is why needle proof vests are so much more expensive - a needle is far more adept at getting through the tiny gaps. A high standard ballistic vest usually has about 14 layers of kevlar in it as well as padding - this at the IIA/B standard is guaranteed to stop a .44 magnum bullet. Beyond that level you are talking about ceramic plating. The way they test against knives is to fire them with about 5 times the force of a very heavy angry person into the vest and see if it goes through. Anyway, specifically for a stab proof hoody - whilst one layer may not be 100% stab proof 100% of the time the areas that are covered are much much less likely to be penetrated with a knife and certainly whilst there would be trauma the chance of you dying or even being bled would drop quite considerably. Yeh it seems like an odd one - but I guess if you were in a situation with someone taking potshots at you it would guard your torso pretty well.
dinner? a nice smile and im already stripping mate. I think i was once called a "hooker" by my girlfriend.
Your a hooker? Props to you. To do the job you need a really good End. Yes, I played rugby. How did you know?