Reverse engineering to class diagram weird associations

I am trying to reverse-engineer a school project into a Class Diagram. I noticed that when it's done, all my associations have this little bullet kind of thing in front of the one-way navigable arrow like this:

enter image description here

What is it and what does it do? Also how do I turn it on or off, or get rid of it?

I would greatly appreciate your help as I cannot find any relevant information on Google and it is due tomorrow to finish it.

Solution

I found it! :D

For some magical reason stackoverflow gave this in related questions: setting the association-end ownership in uml

I didn't know how to describe what I was looking for, ownership is what it is! :)