When Spats Sparkle and Dag replace the diamond with a fake one, Shredder steals it. Shredder brings the fake diamond to the windmill, and attaches it to the Laser Dimension Blade.
After finding out the diamond is a fake, Shredder locates the real diamond, and brings it back to the Laser Dimension Blade in the windmill.
When the Turtles arrive to the windmill, Donatello corrects the beam. He also reserves the pole so instead of pulling the Technodrome to Earth, it pulls the windmill through the portal and towards the Volcanic Asteroid, where it crashes into the Technodrome by breaking through the wall.