How to make Halloween Mask :
Gather one empty, washed gallon milk jug for every two guests. Cut along the side seams of each jug, starting from the mouth of the jug.
Shift direction toward the center of the jug (toward the handle) when the scissors are about even with a point roughly one inch below the handle (the end furthest from the jug mouth). Continue cutting across the jug until you reach the seam on the other side, then cut back up along that seam toward the mouth until the jug is in two pieces. The handle piece, with its built-in "nose," will be smaller.

To finish, cut the mouth part of the jug from each piece, making a slightly rounded cut after it is removed to echo the shape of the chin. Trim any rough edges. On the larger piece, the jug bottom is meant to sit atop the child's head and the longer side against the child's face. Cut the shorter side so the opening is large enough to slide comfortably over a child's head.
Using your child as a model, mark dots on each mask for eyes and mouth holes. Remove the mask, and cut out large eye holes -- at least twice the size of your child's eyes. Make evil upturned eyes, as well as wicked grins, crooked smiles, and gaping-gasp mouths. Tape the outside edges of the mask with colored electrical tape to prevent scrapes or cuts.