How to connect endcap cell vertically in soc encounter?

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  I had some problems with soc encounter's endcap cells.

    In the design, after adding endcap cells to the each end of the row, I want end cells on each row to be connected vertically, for example, left_end_cell1 on row 1 to connect to left_end_cell2 on row 2 and they are both connected to vdd!. 

   As a experiment, I created two cells: ENDCAPL  and ENDCAPR, which contained only nwell, power/ground rails and metal2 pins as vdd! and gnd!, but in soc encounter, when I did sroute, it still route horizontally to the ring, not connecting endcells vertically.

  If I can route power/ground nets like shown in the attached file, then I should use cells as leftend and rightend to do power distribution.
 
 How can I make it connect power/ground nets vertically?

 Thank you very much!