diff --git a/lib/buff/extensions/hash.rb b/lib/buff/extensions/hash.rb
index b69a9c5..ff20281 100644
--- a/lib/buff/extensions/hash.rb
+++ b/lib/buff/extensions/hash.rb
@@ -1,5 +1,12 @@
-require_relative 'hash/dotted_paths'
-require_relative 'hash/except'
-require_relative 'hash/key_transforms'
-require_relative 'hash/reverse_merge'
-require_relative 'hash/slice'
+module Buff::Extensions
+  module Hash
+    require_relative 'hash/dotted_paths'
+    require_relative 'hash/except'
+    require_relative 'hash/key_transforms'
+    require_relative 'hash/reverse_merge'
+    require_relative 'hash/slice'
+
+    extend Slice
+    extend ReverseMerge
+  end
+end
diff --git a/lib/buff/extensions/hash/reverse_merge.rb b/lib/buff/extensions/hash/reverse_merge.rb
index 9f7f1f1..b30d845 100644
--- a/lib/buff/extensions/hash/reverse_merge.rb
+++ b/lib/buff/extensions/hash/reverse_merge.rb
@@ -1,23 +1,43 @@
 module Buff
   module Extensions::Hash
     module ReverseMerge
+      class << self
+        def extended(base)
+          base.extend(ClassMethods)
+        end
+      end
+
+      module ClassMethods
+        # @param [Hash] other
+        #
+        # @return [Hash]
+        def reverse_merge(one, two)
+          two.merge(one)
+        end
+
+        # @param [Hash] other
+        #
+        # @return [Hash]
+        def reverse_merge!(one, two)
+          one.merge!(two) { |key, old, new| old }
+        end
+
+        extend self
+      end
+
       # @param [Hash] other
       #
       # @return [Hash]
       def reverse_merge(other)
-        other.merge(self)
+        ClassMethods.merge(self, other)
       end
 
       # @param [Hash] other
       #
       # @return [Hash]
       def reverse_merge!(other)
-        merge!(other) { |key, old, new| old }
+        ClassMethods.reverse_merge!(self, other)
       end
     end
   end
 end
-
-class Hash
-  include Buff::Extensions::Hash::ReverseMerge
-end
diff --git a/lib/buff/extensions/hash/slice.rb b/lib/buff/extensions/hash/slice.rb
index 4bdef86..7fb8392 100644
--- a/lib/buff/extensions/hash/slice.rb
+++ b/lib/buff/extensions/hash/slice.rb
@@ -3,22 +3,37 @@ module Extensions::Hash
     # Borrowd and modified from
     # {https://github.com/rails/rails/blob/master/activesupport/lib/active_support/core_ext/hash/slice.rb}
     module Slice
+      class << self
+        def extended(base)
+          base.extend(ClassMethods)
+        end
+      end
+
+      module ClassMethods
+        def slice(obj, *keys)
+          obj.keys.map! { |key| obj.convert_key(key) } if obj.respond_to?(:convert_key, true)
+          obj.keys.each_with_object(obj.class.new) { |k, hash| hash[k] = obj[k] if obj.has_key?(k) }
+        end
+
+        def slice!(obj, *keys)
+          obj.keys.map! { |key| obj.convert_key(key) } if obj.respond_to?(:convert_key, true)
+          omit = obj.slice(*obj.keys - keys)
+          hash = obj.slice(*keys)
+          obj.replace(hash)
+          omit
+        end
+
+        def extract!(obj, *keys)
+          obj.keys.each_with_object(obj.class.new) { |key, result| result[key] = obj.delete(key) if obj.has_key?(key) }
+        end
+
+        extend self
+      end
+
       # Slice a hash to include only the given keys. This is useful for
-      # limiting an options hash to valid keys before passing to a method:
-      #
-      #   def search(criteria = {})
-      #     criteria.assert_valid_keys(:mass, :velocity, :time)
-      #   end
-      #
-      #   search(options.slice(:mass, :velocity, :time))
-      #
-      # If you have an array of keys you want to limit to, you should splat them:
-      #
-      #   valid_keys = [:mass, :velocity, :time]
-      #   search(options.slice(*valid_keys))
+      # limiting an options hash to valid keys before passing to a method
       def slice(*keys)
-        keys.map! { |key| convert_key(key) } if respond_to?(:convert_key, true)
-        keys.each_with_object(self.class.new) { |k, hash| hash[k] = self[k] if has_key?(k) }
+        ClassMethods.slice(self, *keys)
       end
 
       # Replaces the hash with only the given keys.
@@ -27,11 +42,7 @@ def slice(*keys)
       #   { a: 1, b: 2, c: 3, d: 4 }.slice!(:a, :b)
       #   # => {:c=>3, :d=>4}
       def slice!(*keys)
-        keys.map! { |key| convert_key(key) } if respond_to?(:convert_key, true)
-        omit = slice(*self.keys - keys)
-        hash = slice(*keys)
-        replace(hash)
-        omit
+        ClassMethods.slice!(self, *keys)
       end
 
       # Removes and returns the key/value pairs matching the given keys.
@@ -39,12 +50,8 @@ def slice!(*keys)
       #   { a: 1, b: 2, c: 3, d: 4 }.extract!(:a, :b) # => {:a=>1, :b=>2}
       #   { a: 1, b: 2 }.extract!(:a, :x)             # => {:a=>1}
       def extract!(*keys)
-        keys.each_with_object(self.class.new) { |key, result| result[key] = delete(key) if has_key?(key) }
+        ClassMethods.extract!(self, *keys)
       end
     end
   end
 end
-
-class Hash
-  include Buff::Extensions::Hash::Slice
-end