Instructions
Start ̶0;Halo 3̶1; and select ̶0;Forge̶1; from the main menu of the game.
Click on the ̶0;Usermap Mod̶1; option and choose ̶0;Sandtrap̶1; as your map.
Scroll through the map until you get to the area with the frigate in the sky.
Select any item from the items pane to add it to the map. Drag it underneath the frigate.
Click on the item to select it and then select the ̶0;Swap item̶1; option.
Select the frigate from the list of items to swap them. The frigate will now be moved down.
Save your changes and load the Sandtrap map in the main game. Walk over to the area where the frigate is; you will notice it has been moved to the ground. Press the ̶0;Jump̶1; button to climb inside it.