When you start this mission you should be to the right of the large protective screen. If you go forward slightly you should see a platform to your right. Use a Jet Pack to get up there. There should be a weapon crate up there. If you collect this crate you will get 25 Sentry Guns. Use these on a flat piece of ground. Then at your next turn, go close to the Sentry Gun and fire it at an enemy worm. The Sentry Gun should detect this and will fire lots of bullets at the worm you shot. Note: You can only use one Sentry Gun at a time until it is destroyed; place it carefully. Also, this is not the only other time in the game you can use a Sentry Gun. The other is on the final level, where you only have two of them.