Quote:
Originally Posted by sugarwood
Dumb question, but why can't you just turn your head?
Hiding from German troops with mustard gas in those orthogonal trenches?
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you can turn your head but this thing can make you look left and right
at the same time... that would be painful if you tried it by just turning your head...
(dual prism, one will give an image of the left side, the other of the right side)
Very useful for setting out lines and 90 degree angles.
They are kinda obsolete now but still have there uses here and there.