Is the 20-001 installed at the top or bottom of the sash?

A handy person from Wisconsin says:
Is the tension spring 20-001 secured at the top of the sash or the bottom of the sash?
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Dave Sr. from SWISCO responded:
The 20-001 is installed on the top of the bottom sash and the bottom of the top sash. If it is installed on the top of the top sash it will interfere with the chain pulley in the track.
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