How to separate blocks on right sidebar

Hello,

This is a support request.

I would like to know how can i create a thin horizontal line between every block on my Right sidebar.

I have tried messing around with the CSS file, adding "border-bottom" here and there but no success so far :(

I did manage to increase the margin between them, i found that "1em" was too little for me so I changed to:

.block {
	margin-bottom: 2em;

That works fine. Now i would like to add the line/border, just to make it easier to separate the various blocks.