diff --git a/doc/hook/hook.md b/doc/hook/hook.md
index 3deedfc..8b30332 100644
--- a/doc/hook/hook.md
+++ b/doc/hook/hook.md
@@ -260,4 +260,12 @@ only the game run in that session. A good reference for this might be the variou
 If you have a multi-monitor setup, things are getting quite complicated. Therefore, we are not covering this in here.
 
 Also note that if you want the game to render at a higher resolution than its defined one, e.g. 640x480, this is not
-possible right now. The output you get from the frame buffer will always be its native resolution.
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+possible right now. The output you get from the frame buffer will always be its native resolution.
+
+### The game window is small and the 4:3 games are stretched when full screen on modern widescreen displays
+On supported games, you can change the option `gfx.scaling_mode` in the `hook.conf` file to enable different pre-defined
+scaling modes. Especially for the SD 640x480 4:3 games, this allows you to upscale the rendered output to a widescreen
+display resolution while keeping the aspect ratio (pillarbox).
+
+Note: This does not change the enhance the image quality. It just uses the GPU to interpolate the lower resolution
+output and stretches it to the target surface area.
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