Make Applescript press LShift Exactly what the title says...

I'm new to coding and I am trying to make AppleScript simulate the key press of LShift. When I run the program, there seems to be a delay, indicating that it may be actually pressing LShift, but I tried a virtual keyboard tester, and it does not indicate LShift being pressed... I am not sure how to make the program. Help would be greatly appreciated.

Thanks

Edit: Basically, I want AppleScript to press Shift (on the left). I don't know what the coding for this part is.

This is my code so far:

    repeat
       repeat 5 times
          tell application "System Events"
             keystroke "r"
             delay 5
          end tell
       end repeat
       repeat 10000 times
          tell application "System Events"
             keystroke using {shift down}
          end tell
       end repeat
    end repeat


I don't know whether pressing "keystroke using {shift down} actually is pressing shift.
I think you want this

tell application "System Events"
    key code 56
end tell