Australian1 term for the little
cardboard scroll at the end of a
joint. In the
United States and Britain this is often called a
roach, but a roach is also used to refer to the end of a joint after as much as possible/desired has been consumed.
Scrollies are also often known as filters, even though no actual filtering takes place - a better term might be handle or holder. The purpose of the scrollie is to ensure that air is free to pass through the joint. Without it, one would crush and/or excessively wet the end, making smoking unpleasant or impossible.
Note that a scrollie is not necessary or even desirable when one is smoking a joint of pure weed.
1. possibly used elsewhere too. Scrollie rhymes with rollie.