The thickness tool adds or removes material to or from a face, in order to increase order to decrease its size.
It can be used as a quick way to change the size of a local feature on a solid body without having to first create a sketch. It is also used to extend the size of the solid with complex profiles, such as a spline or surface, so it can follow the shape.
The thickness tool can be found under the “Dress-Up Features” toolbar, shown below;
Before using the tool, make sure you have a suitable part already loaded;
Then select the tool; you should see the following dialogue box;
Here, you can enter the desired thickness for a surface of your choice. You will have to select this surface using the dialogue box. Also, you have to select the surfaces where this thickness will be added. A preview of the effect can be seen before clicking ok.