39-020 vs 39-021, Right vs Left Cranks
A purchasing agent from California says:
January 26, 2012
Tom from SWISCO responded:
January 27, 2012
Thanks for posting. This is a good question.
The reason why we don't specify which operator is left and which is right is because the right and left hand sides vary from manufacturer to manufacturer. Some companies define the way the window opens as left or right, while others define which side the operator sits on as left or right.
The best way to tell which arm is right and which is left for your specific window--and not a generalized standard--is to look at your existing operators and match them up with our pictures of the 39-020 and 39-021 on our site.
I hope this information helps you!