diff --git a/app/Main.hs b/app/Main.hs
index 66768c3..d7ab520 100644
--- a/app/Main.hs
+++ b/app/Main.hs
@@ -12,7 +12,7 @@ module Main
 
 -- base
 import Control.Monad
-  ( void )
+  ( void, when )
 import Data.Foldable
   ( for_ )
 import Data.Int
@@ -181,6 +181,7 @@ main = do
   modeTVar           <- STM.newTVarIO @Mode                         Path
   partialPathTVar    <- STM.newTVarIO @( Maybe PartialPath )        Nothing
   fileBarTabsTVar    <- STM.newTVarIO @( Map Unique GTK.Box )       Map.empty
+  showGuidesTVar     <- STM.newTVarIO @Bool                         True
 
   -- Put all these stateful variables in a record for conciseness.
   let
@@ -297,15 +298,17 @@ main = do
       mbHoldAction   <- STM.readTVar mouseHoldTVar
       mbPartialPath  <- STM.readTVar partialPathTVar
       mode           <- STM.readTVar modeTVar
+      showGuides     <- STM.readTVar showGuidesTVar
       pure do
         renderDocument
           colours mode ( viewportWidth, viewportHeight )
           mbMousePos mbHoldAction mbPartialPath
           doc
-        renderGuides
-          colours ( viewportWidth, viewportHeight ) ViewportOrigin ( viewportWidth, viewportHeight )
-          mbMousePos mbHoldAction
-          doc
+        when showGuides do
+          renderGuides
+            colours ( viewportWidth, viewportHeight ) ViewportOrigin ( viewportWidth, viewportHeight )
+            mbMousePos mbHoldAction
+            doc
     case mbRender of
       Just render -> Cairo.renderWithContext render                  ctx
       Nothing     -> Cairo.renderWithContext ( blankRender colours ) ctx
@@ -324,11 +327,13 @@ main = do
       mbRender <- STM.atomically $ withCurrentDocument variables \ doc@( Document {..} ) -> do
         mbMousePos     <- STM.readTVar mousePosTVar
         mbHoldAction   <- STM.readTVar mouseHoldTVar
+        showGuides     <- STM.readTVar showGuidesTVar
         pure do
-          renderGuides
-            colours ( viewportWidth, viewportHeight ) ( RulerOrigin ruler ) ( width, height )
-            mbMousePos mbHoldAction
-            doc
+          when showGuides do
+            renderGuides
+              colours ( viewportWidth, viewportHeight ) ( RulerOrigin ruler ) ( width, height )
+              mbMousePos mbHoldAction
+              doc
       for_ mbRender \ render -> Cairo.renderWithContext render ctx
 
       pure True
diff --git a/assets/theme.css b/assets/theme.css
index 540d06a..a5902ca 100644
--- a/assets/theme.css
+++ b/assets/theme.css
@@ -76,7 +76,7 @@
   background-color: rgba(48, 45, 38, 0.66);
 }
 .guide {
-  color: rgba(28, 196, 79, 0.66)
+  color: rgba(28, 196, 79, 0.4)
 }
 .magnifier {
   color: rgb(236, 223, 210);
diff --git a/src/app/MetaBrush/Action.hs b/src/app/MetaBrush/Action.hs
index 7e87165..5547a6b 100644
--- a/src/app/MetaBrush/Action.hs
+++ b/src/app/MetaBrush/Action.hs
@@ -482,6 +482,20 @@ instance HandleAction Delete where
                 pure ( UpdateDocTo $ Just ( deleteSelected mode doc ) )
           _ -> pure ()
 
+-------------------
+-- Toggle guides --
+-------------------
+
+data ToggleGuides = ToggleGuides
+  deriving stock Show
+
+instance HandleAction ToggleGuides where
+  handleAction ( UIElements { viewport = Viewport {..} } ) ( Variables { showGuidesTVar } ) _ = do
+    STM.atomically $ STM.modifyTVar' showGuidesTVar not
+    GTK.widgetQueueDraw viewportDrawingArea
+    for_ [ rulerCornerDrawingArea, topRulerDrawingArea, leftRulerDrawingArea ] \ drawingArea -> do
+      GTK.widgetQueueDraw drawingArea
+
 ------------
 -- Confirm --
 ------------
@@ -659,16 +673,18 @@ instance HandleAction MouseClick where
                   _ -> pure Don'tModifyDoc
 
             RulerOrigin ruler -> do
-              let
-                mbGuide :: Maybe Guide
-                mbGuide = selectGuide pos doc
-                guideAction :: GuideAction
-                guideAction
-                  | Just guide <- mbGuide
-                  = MoveGuide ( guideUnique guide )
-                  | otherwise
-                  = CreateGuide ruler
-              STM.writeTVar mouseHoldTVar ( Just $ GuideAction { holdStartPos = pos, guideAction } )
+              showGuides <- STM.readTVar showGuidesTVar
+              when showGuides do
+                let
+                  mbGuide :: Maybe Guide
+                  mbGuide = selectGuide pos doc
+                  guideAction :: GuideAction
+                  guideAction
+                    | Just guide <- mbGuide
+                    = MoveGuide ( guideUnique guide )
+                    | otherwise
+                    = CreateGuide ruler
+                STM.writeTVar mouseHoldTVar ( Just $ GuideAction { holdStartPos = pos, guideAction } )
               pure Don'tModifyDoc
 
       -- Right mouse button: end partial path.
diff --git a/src/app/MetaBrush/Context.hs b/src/app/MetaBrush/Context.hs
index f053d44..b475183 100644
--- a/src/app/MetaBrush/Context.hs
+++ b/src/app/MetaBrush/Context.hs
@@ -108,6 +108,7 @@ data Variables
   , modeTVar           :: !( STM.TVar Mode                         )
   , partialPathTVar    :: !( STM.TVar ( Maybe PartialPath )        )
   , fileBarTabsTVar    :: !( STM.TVar ( Map Unique GTK.Box )       )
+  , showGuidesTVar     :: !( STM.TVar Bool                         )
   }
 
 --------------------------------------------------------------------------------
diff --git a/src/app/MetaBrush/Render/Document.hs b/src/app/MetaBrush/Render/Document.hs
index 8d9fee1..f8a9656 100644
--- a/src/app/MetaBrush/Render/Document.hs
+++ b/src/app/MetaBrush/Render/Document.hs
@@ -360,7 +360,7 @@ renderGuide ( Colours {..} ) zoom ( Guide { guidePoint = Point2D x y , guideNorm
   Cairo.translate x y
   Cairo.scale ( 1 / zoom ) ( 1 / zoom )
 
-  Cairo.setLineWidth 2.0
+  Cairo.setLineWidth 1.5
   withRGBA guide Cairo.setSourceRGBA
 
   Cairo.moveTo (  1e5 * ny ) ( -1e5 * nx )
diff --git a/src/app/MetaBrush/UI/Menu.hs b/src/app/MetaBrush/UI/Menu.hs
index a1a8c0d..fd22e8f 100644
--- a/src/app/MetaBrush/UI/Menu.hs
+++ b/src/app/MetaBrush/UI/Menu.hs
@@ -158,6 +158,8 @@ data ViewMenu ( rt :: ResourceType )
   , metaparameters :: !( MenuItem () NoSubresource rt )
   , viewSep2       :: !( Separator rt )
   , transform      :: !( MenuItem () NoSubresource rt )
+  , viewSep3       :: !( Separator rt )
+  , guides         :: !( MenuItem ToggleGuides NoSubresource rt )
   }
   deriving stock Generic
 
@@ -216,6 +218,8 @@ viewMenuDescription
   , metaparameters = MenuItemDescription  "Metaparameters" [ "submenuItem" ] () Nothing NoSubresource
   , viewSep2       = SeparatorDescription                  [ "submenuSeparator" ]
   , transform      = MenuItemDescription  "Transform"      [ "submenuItem" ] () Nothing NoSubresource
+  , viewSep3       = SeparatorDescription                  [ "submenuSeparator" ]
+  , guides         = MenuItemDescription  "Guides"         [ "submenuItem" ] ToggleGuides ( Just ( GDK.KEY_G, [] ) ) NoSubresource
   }
 
 helpMenuDescription :: HelpMenu Description