[Samw]

You should have 3 "arms". 2 of them are double ended and one of them is single ended.

For once a day, install the arm with 1 end.
For twice a day, install the arm with 2 ends.
For 3 times a day, install the arm with 1 end plus 1 of the arms with 2 ends.
For 4 times a day, install both arms with 2 ends.