Beezer. You just get about a 10"square of cornflake packet, crease it diagonally to triangular, open it out again, then get a 9"square of strong brown parcel paper crease it similarly and glue it to two sides of the card board straddling the crease; tuck it in; it's done. To work it, hold by the end of the 'banger' opposite the brown paper, raise your arm and bring it sharply down.. Sometning like that i think :-)