All you need is 2 players and a machine gun turret.

Put down a turret and have one player look straight up. Have 1 person go to forge (flying mode) and pick up the turret with the other player.

Go to almost any glass window and put the turret on the window. The person should be outside the glass.

They should see you through the glass, if not then it wont work.

If they do, then have them go into forge mode while looking up, they should be outside the window.

Examples: Foundry, Rats Nest, Avalanche.