I know that my brother is using drugs but not sure what kind. I keep find rolled up cardboard always in about 1 1/2-2 inch diameter. What could this be used for? I can't smell anything on it. Sometimes there are burn marks on it.

Well, if you take a piece of aluminum foil and combine cocaine, baking soda, and a bit of water and rub it all over to make it kind of pasty then let it dry it makes a kind of crack type thing. You then use a lighter underneath the foil and burn the paste off and you inhale it through the tube. I could be way off on this but it sounds about right.

Not really familiar with this description of the cardboard.

Old days used tubes(paper towel tubes,etc) and foil for improvised pipes,but you would have seen a depression or cut out in them.

No angle?Just a straight piece of cardboard rolled up?IDK.

A toilet paper roll was common for this or a top off a water bottle.

New scene,new ways.

Could also be used for huffing.