HABTM Checkboxes using simpleform gem - ruby-on-rails-3

Question

I have three models, and i am trying to save onto a third table using simple form gem and checkboxes.
class Work < ActiveRecord::Base
has_many :skills, through: :skillships
end
The second model is
class Skill < ActiveRecord::Base
has_many :works, through: :skillships
end
The third is
class Skillship < ActiveRecord::Base
belongs_to :work
belongs_to :skill
end
Using the Work model i am trying to save the data on the skillship table. Something similar to this http://railscasts.com/episodes/17-habtm-checkboxes-revised. Can you please help.
EDIT
The form
<%= simple_form_for(#work) do |f| %>
<%= f.error_notification %>
<div class="form-inputs">
<%= f.input :title, :label => 'Project Title' %>
<%= f.input :excerpt, :as => :text %>
<fieldset>
<legend>Skills Used </legend>
Would like to check the skills i used here.
</fieldset>
</div>
<div class="form-actions">
<%= f.button :submit %>
</div>
<% end %>
I tried..
<%= hidden_field_tag "work[skill_ids][]", nil %>
<% Skill.all.each do |skill| %>
<%= check_box_tag "work[skill_ids][]", skill.id, #work.skill_ids.include?(skill.id), id: dom_id(skill) %>
<%= label_tag dom_id(skill), skill.title %><br>
<% end %>
The reason i'm doing this it because work can have many skills used.

Answer 1

I was going about this the wrong way. A join table solved the problem.
rails g migration create_skills_works_table
Then
class CreateSkillsWorksTable < ActiveRecord::Migration
def self.up
create_table :skills_works, :id => false do |t|
t.references :skill
t.references :work
end
add_index :skills_works, [:skill_id, :work_id]
add_index :skills_works, [:work_id, :skill_id]
end
def self.down
drop_table :skills_works
end
end
Using simple form on the work view.
<fieldset>
<legend>Skills Used </legend>
<%= f.association :skills %>
</fieldset>