I need to make a LINE with a rounded edge but the properties "Corners" > Rounded isn't working

Hi there, 

I can only find tutorials online for making rounded edges on a rectangle, and that works fine with corners in the property. 

I need to make a straight line with rounded edges on both ends and for that, the properties>corners>rounded does not work. I've tried 50px or 2px for a line that is 2px wide and literally nothing works, they stay sharp as a razor blade. 

Thanks for your help!