For old rangefinders, the must have tip

The Kodak Retinaii is a rangefinder and an old one.
Sometimes focusing is very hard because the rangefinder square is small unlike the Leica’s M9.
After much cleaning up and reading, i came across this tip published in a rangefinder forum.

I tried it and…kazam! Focusing has suddenly improved dramatically. The tip is a very simple idea.
Cut a square black tape and stick it to the viewfinder, the size preferably should be near the rangefinder other “window” that you move to focus.
By blocking the main viewfinder with a corresponding square, when you move the rangefinder window, its so much easier to see.

Try it today, it might change the way you look at old rangefinder cameras. I tried it in low light and other scenario, it has my vote as the no.1 tip of all time for rangefinder camera.