When you have an object moving in an animation and you want the object to slow down, stop and stay still for a while, before it moves off again, you can run into an “overshoot” problem. This is when the object seems to shoot past where you want it to stop and it doesn’t stop ..
There are several ways to add thickness to objects. One way is to use Explosion FX. The nice thing about this is that you can adjust the thickness later on if you change your mind about how thick it should be, whereas if you’ve added thickness via polygon modeling, it can take longer to adjust ..