namespacing.rb

# config/routes.rb
namespace :admin do 
  resources :boats
  resources :stuff
end

# app/controllers/admin_controller.rb
# This controller just refactors all shared logic for admin-namespaced controllers
class AdminController < ApplicationController
  # If multiple models:
  before_filter :authenticate_admin!
  # If admin flag:
  before_filter :check_user_is_admin
  
  def check_user_is_admin
    unless current_user.admin?
      redirect_to root_path, notice: t("notices.action_not_allowed")
    end
  end
end

# app/controllers/admin/boats_controller.rb
# Make sure all admin-namespaced controllers inherit from the AdminController 
class BoatsController < AdminController
  respond_to :html
  
  def index
    @boats = Boat.all
    respond_With @boats
  end
  
  # ... and whatever you may want... #
end