Indent Excerpt on Main Page

I’m using the Iridium theme, and on the default, it seems that the author managed to allow all the posts on the main page to be indented slightly, lining them with the comment dividing bar.

Now that I’ve started adding things to the loop, it seems that the indentation command has dissapeared.

I’ve been comparing notes, and I just can’t find out what command allowed him to do that… I’d like to be able to do the same thing, allowing my excerpts to be indented like on the default.

Anyone know the command for this?