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1 Man
3 Chairs
1 120" Electric Screen.
Position a chair underneath the two mounts. Finger tight the bolts that hold the screen to the mounts with just enough clearance to get screen in still.
Put other chair in the middle.
Grab the screen in both hands. take steady steps to the middle chair. take a step up onto the chair and steady yourself.
Raise the screen up and into the mounts.
Now this is the good bit. Get one hand dead centre of the screen. Move one leg across to the chair on the right (or left) Move other hand over towards the mount bolt. Pray to god you are strong enough to hold the screen up and can move with the speed and agility of the flash.
finger tighten the bolt so it goes under the screen lip and holds the screen up on that side. move back to middle chair. go the opposite way and finger tighten the other bolt so it goes under the lip of the screen.
this should (mine did) take the weight of the full screen.
gingerly let go.
now move like the wind get the screwdrive and tighen each bolt up as tight as it will go on both sides.