How can I make some edges on my model sharper and others more rounded? I have an image explanation of what I want to achieve. Here it is:


Right now the whole edge is sharp. It is giving me a really hard time.
Also here is the model:
https://www.dropbox.com/s/zvempvps0r4815j/glock_forum2.blend

Thanks in advance :)
Mean Crease

I think the function you are looking for is called Mean Crease. It makes sharper edges when you are using a Subsurface modifier for example. Here's how it's used:  

  

If you want, once you have the edges selected in Edit mode, instead of manually adjusting the Mean Crease value as shown above, you can use the keyboard hotkeys for Mean Crease with the mouse:
SHIFTE -> drag the mouse