how to set the value of my checkbox?

hey all,
I'm have a HABTM relationship and I'm trying to use checkbox.
The problem is that I can't set the value of each checkbox sad each
checkboth value gets set either to 1 or 0 depending on whether the it
is checked or not. I would like the value to be equal to the id of my
This is how I do it:

<% for cat in @categories %>
<p><b><%=></b> <br />
<% for forum in cat.forums %>
<%= check_box(:forums, :id ,:value=>, :checked =>
(forum.users.include? @user) ? 'checked' : false ) %><%=
forum.forum_name %> <br />

<% end %>
<% end %>

I also tried without the :value=> but still nothing

Any idea?

thanx in advance