40 2-inch high Dixie cups per patrol.
A judge with an 18 inch ruler, preferably one judge for each patrol.

The quickest patrol to build an 18-inch high building wins.

Define a starting line behind which each patrol lines up.
Place a neat stack of each patrol's 40 cups out about 20 feet from the start line.
On 'Go', the first scout in each patrol runs to his stack of cups, removes one and sets it on the floor, and runs back to tag the next in line.
Each scout adds one cup in whatever way he chooses to his patrol's building and returns, as quickly as possible.

If a building falls over, the patrol can choose to keep using the existing building or have a scout use his turn to put all the cups back in the stack and start over.