Here is a quote from Bertrand Russell's The Practice and Theory of Bolshevism.
I have never met a personage so destitute of self-importance. He looks at his visitors very closely, and screws up one eye, which seems to increase alarmingly the penetrating power of the other.
I can't imagine what "screws up one's eyes" looks like. It is even more difficult to imagine "screw up one eye." I think only ostensive definition can help. Please kindly provide a picture.