You'll need 3 screws to install the landing gear at a precise position, so that the rubber band will hit the Z stepmotor corner when the printing bed support will fall at the end of each printing.
Check out the pictures : it's meant to be installed very close to the further support part of the left slideZ piece. I've made if with a corner to fit exactly this part, and there even are two lines engraved on it, that point to the center of that further left screw. If you place it precisely there, the arms of the landing gear should fall exactly at the right place, by the sides of the stepmotor.
Install thightly a thick rubber band there so that when the bed will fall, it will keep it (that's the general idea) from falling lower and hit anything.
That should do the trick. :)