Answer:
Each of these ends in a kettle full of precious metal and the double variety is quite awesome
I open wide and tight I shut, Sharp am I and paper-cut fingers too, so do take care, I'm good and bad, so best beware.
Runs over fields and woods all day. Under the bed at night sits not alone, With long tongue hanging out, Resting at your feet until we go for a walk
I am believed to be only one dimensional, and tinier than anything can be, and there are many who say that I am the basis of all that we see. What am I?
All about, but cannot be seen, Can be captured, cannot be held, No throat, but can be heard.
Long and slinky like a trout, never sings till it's guts come out.