I'm setting up an option for users to filter message board threads by general topics. For example, if it were WebmasterWorld then they might filter "HTML", "CSS", and "Javascript" to see all post in those threads on one page.

But I need to come up with an icon for this that would make sense to the below average user.

Mobile users are the biggest obstacle, as I have AT MOST 100px in width to spare, but preferably only around 30px for it to look right. So I really need just an icon without the use of explaining text.

I can imagine that one could refer to these topics as "topics", "tags", or "filters". So my first thought was an equalizer type icon:

[123rf.com...]

but I'm not sure if a 17 year old student or a 60 year old retired factory worker is going to understand that.

I've always just placed a down-arrow next to the title, thinking that was universal, but literally NOBODY understood it. So I don't think that my second thought of following Facebook's lead and putting ... next to the title would really work, either.

I could probably get away with just saying "Filters" and then a down arrow, but I'd really like to have something a little more attractive.

Can you guys and gals suggest a general icon that would make sense to everyone? I know, I know, KISS...