The better way would be to call the partials from index.html.erb
<% unless params[:check].nil? %>
<%= render :partial => '/layout/check' %>
<% else %>
<%= render :partial => '/layout/not_check' %>
<% end %>
so your def index would look like this
def index
respond_to do |format|
format.html
end
end
I did not understand what you are trying to do but partial which are related to controller/actions should not be in layout unless they are serving some layout.