There are many ways to weigh down your kite. This is just one way important to make sure it is fins up. Other ways are with sand, tie off to the pump attachment or put your board against the L.E behind the kite. Make sure there are no sharp objects that can cause damage to the canopy or L.E.
***** I know but, would you not suggest setting it down a little more gently than at 2:48 ... the corners of the board are almost as sharp as the fins .... just saying