diff --git a/Rules b/Rules
index 697f8d3..ed05db5 100644
--- a/Rules
+++ b/Rules
@@ -20,16 +20,15 @@ tidy       = `which tidy || which tidy5`.chomp
 buildenv   = ENV["buildenv"] || "development"
 
 ##
-# DSL extensions
-Nanoc::RuleDSL::CompilationRuleContext.prepend(Nanoc::RuleDSL::Filter)
-Nanoc::RuleDSL::CompilerDSL.prepend(Nanoc::RuleDSL::RequireRules)
+# Extensions
+Nanoc::RuleDSL::CompilationRuleContext.prepend(Nanoc::Extension::AnonymousFilter)
+Nanoc::RuleDSL::CompilerDSL.prepend(Nanoc::Extension::RequireRules)
 
 ##
 # Plugins
 Nanoc::Webpack
   .default_argv
   .replace([*Nanoc::Webpack.default_argv, "--config", "webpack.#{buildenv}.js"].uniq)
-
 Nanoc::Tidy
   .default_argv
   .replace([*Nanoc::Tidy.default_argv, "--config", "webpack.#{buildenv}.js"].uniq)
diff --git a/nanoc/lib/nanoc/extension/anonymous_filter.rb b/nanoc/lib/nanoc/extension/anonymous_filter.rb
new file mode 100644
index 0000000..15e1664
--- /dev/null
+++ b/nanoc/lib/nanoc/extension/anonymous_filter.rb
@@ -0,0 +1,42 @@
+# frozen_string_literal: true
+
+module Nanoc::Extension
+  ##
+  # The AnonymousFilter extension adds support for Proc-based
+  # filters. See the Rules file to learn how this module is
+  # added to nanoc.
+  module AnonymousFilter
+    require "securerandom"
+    ##
+    # @example
+    #   compile "/sitemap.xml.erb" do
+    #     filter(:erb)
+    #     filter Proc.new { _1.each_line.reject { |s| s.strip.empty? } }
+    #     write("/sitemap.xml")
+    #   end
+    # @param [Proc, Symbol] fn
+    #  Symbol, or Proc for an anonymous filter
+    # @param [Hash] options
+    #  Filter options
+    # @return [void]
+    def filter(fn, options = {})
+      if Proc === fn
+        id = anonymous_id
+        Nanoc::Filter.define(id) { fn.call(_1, _2) }
+        super(id, options)
+      else
+        super(fn, options)
+      end
+    end
+
+    private
+
+    def anonymous_id
+      [
+        "__nanoc",
+        item.identifier.to_s.gsub(%r{[./\\]}, "_")[/[A-Za-z0-9_]+/],
+        SecureRandom.alphanumeric
+      ].join("_").to_sym
+    end
+  end
+end
diff --git a/nanoc/lib/nanoc/ruledsl/require_rules.rb b/nanoc/lib/nanoc/extension/require_rules.rb
similarity index 71%
rename from nanoc/lib/nanoc/ruledsl/require_rules.rb
rename to nanoc/lib/nanoc/extension/require_rules.rb
index 5880ceb..3d0c7ab 100644
--- a/nanoc/lib/nanoc/ruledsl/require_rules.rb
+++ b/nanoc/lib/nanoc/extension/require_rules.rb
@@ -1,20 +1,19 @@
 # frozen_string_literal: true
 
-module Nanoc::RuleDSL
+module Nanoc::Extension
+  ##
+  # The RequireRules extension adds a method that can help
+  # break up the Rules file into multiple separate files.
+  # See the Rules file to learn how this module is added
+  # to nanoc.
   module RequireRules
     ##
     # @example
     #   require_rules "nanoc/rules/assets"
-    #
+    #   require_rules "nanoc/rules/index", {locales: ["en", "ar", "fa"]}
     # @param [String] path
-    #  The path to a file
-    #
     # @param [Hash] locals
-    #  A hash of locals
-    #
     # @param [Binding] target
-    #  Binding context
-    #
     # @return [void]
     def require_rules(path, locals = {}, target = binding)
       locals.each { target.local_variable_set(_1, _2) }
diff --git a/nanoc/lib/nanoc/ruledsl/filter.rb b/nanoc/lib/nanoc/ruledsl/filter.rb
deleted file mode 100644
index 5cb9c93..0000000
--- a/nanoc/lib/nanoc/ruledsl/filter.rb
+++ /dev/null
@@ -1,38 +0,0 @@
-# frozen_string_literal: true
-
-module Nanoc::RuleDSL
-  module Filter
-    ##
-    # @example
-    #   compile "/sitemap.xml.erb" do
-    #     filter(:erb)
-    #     filter Proc.new { _1.each_line.reject { |s| s.strip,empty? } }
-    #     write("/sitemap.xml")
-    #   end
-    #
-    # @param [Proc, Symbol] fn
-    #  The name of a Symbol, or Proc for an anonymous filter
-    #
-    # @param [Hash] options
-    #  Filter options
-    #
-    # @return [void]
-    def filter(fn, options = {})
-      if Proc === fn
-        id = random_id
-        Nanoc::Filter.define(id) { fn.call(_1, _2) }
-        super(id, options)
-      else
-        super(fn, options)
-      end
-    end
-
-    private
-
-    def random_id
-      name = item.identifier.to_s.gsub(%r{[./\\]}, "_")[/[A-Za-z0-9_]+/]
-      random = SecureRandom.alphanumeric
-      :"__nanoc_#{name}_#{random}"
-    end
-  end
-end