It means that, that particular club is a hells Angel supporter
Yellow Hammer is a term for a curve ball that not only breaks but has a big drop to it. Another term for Yellow Hammer is a '12 to 6' curve ball. Other terms for a curve ball are 'yakker' and 'Uncle Charlie'.
Means they aint scared to fight
Please re-define question: do you mean ball-peen hammer, bullpen (as in baseball) or ball-point pen, or something completely different?
I'm going to assume you mean a ball peen hammer. They're commonly used by mechanics, for instances where metal plates or panels have to be hammered back into shape.
In the classic "rumbles" of the 1950's, motorcycle chains and sometimes spud wrenches were carried for use as weapons under the legitimacy of also being used to make repairs. The ball peen hammer replaced these implements and became so popular with the club some support items bear a single hammer or two crossed hammers. One cannot be arrested for illegal possession of a hammer.
In what context? I would think it means you can't wear jeans or jackets.
Letterman jacket
Odin didn't have a hammer. His son Thor had the hammer Mjolnir.
hammer?if you mean one its hammer
ham in german is schinken
If the motorcycle is a Kawasaki, then likely that's the model.
They would be the "Hells Angels" motorcycle group.