How RoR extract a http parameterfrom arequest?

This is request made from the client:
new Ajax.Updater("sip_tab_content",
           "/rails/test_modules/show/"+$F"boardid"),
                    {method :'get',
                      onFailure:displaySIPTabFailure,
                      onComplete:displaySIPTabFailure
                    });

This is controller from the ROR controller acting as server:
class TestModulesController < ApplicationController
def index
    @test_modules = TestModule.find(:all)

    respond_to do |format|
      format.html # index.html.erb
      format.xml { render :xml => @test_modules }
    end
  end
def show
    @test_module = TestModule.find(params[:id])
#TestModule is a module class accessing database
    respond_to do |format|
      format.html # show.html.erb
      format.xml { render :xml => @test_module }
    end
  end
end
# index.html.erb:

The parameter value "($F"boardid")" passed by Ajax.Updater is taken by
"id". I'm a newbie and didn't know how the "($F"boardid")" is passed
into "id". If I want to add one para after "($F"boardid")" , how to pick
it from controller?