What car and motor are you trying to start up.

Off the bat, loosen the 4 holding screws that keep the four rubber tabs in place. Move these tabs to their furthest outward positions.

Now put the car on the starter and make sure the starter wheel lines up perfectly with your flywheel. Now push the four rubber tabs back into place against the frame of your car, making sure the car doesn't move anywhere. Now tighten the screws back up. This will ensure you car lines up perfectly every time and doesn't move around.

Let us know how it goes and good luck.