Brief summary; for Toro TFS-075 installation, put the round pin in the round hole (not the slot).
Toro TFS-075: “Carefully line up the guide pin on the sensor to the slot on the tee.”
Badger Series 735: “Insert the sensor into the tee, carefully lining up the locating hole in the sensor with the locating pin in the tee.”
As a system upgrade, I installed a TFS-075 sensor for use with my Rachio 2 controller. After several iterations, I was finally able to get the Rachio / flow sensor combination working correctly. One problem was a Rachio issue, reversed K and Offset values for the TFS-075. But the other problem was TFS-075 installation guidance; “Carefully line up the guide pin on the sensor to the slot on the tee.” The brief summary is that the pin/location hole setup in the guide does not match the TFS-075 (Badger). See above photographs.
Only after reading the Badger Series 735 instructions was I able to make sense of the installation process. “Insert the sensor into the tee, carefully lining up the locating hole in the sensor with the locating pin in the tee.”