In this exercise you'll learn about the feature Boss.
With that you can create sections of shafts or add cylindrical attachments to surfaces.
Open the model cylinder, if you created it before, and save it as boss according to the naming convention. If you did not create it previously, create a new model with the name boss and add a cylinder with the following dimensions to it:
| Dimension | Value [mm] |
|---|---|
| Diameter | 20 |
| Height | 50 |
(refer figure "basic body cylinder")
Now click the feature Boss 
.
In the window Boss enter these values for diameter and height:
| Dimension | Value [mm] |
|---|---|
| Diameter | 10 |
| Height | 20 |
Select one of the two flat surfaces of the cylinder to position the boss. Confirm by clicking OK.
The Boss should now appear on the selected surface. (refer figure "boss added")
Now you have to position the boss in the window Positioning.
Select the option 
(Point onto Point).
Click the outer edge of the cylinder to create this reference.
Now the window Set Arc Position pops up, in which you have to set a precise selection. Click Arc Center, which finishes positioning.
Create the same boss on the opposite side of the cylinder. (refer figure "second boss added")