My crews used to install gable trusses by nailing a piece of two-by lumber to the gable wall of the house in such a way that it stuck up high enough to catch the top chord of the truss when we rolled it. The two-by, which was braced to a stake in the ground, prevented the truss from going beyond 90 degrees and toppling off the end of the building.
Then I came up with a trick that makes it faster and safer to install these trusses. Instead of standing a single truss against a vertical two-by, we create a wide stable base by nailing spacers between the first two trusses and standing them as a single unit. As long as it's not too windy, the truss unit will sit upright on the walls.
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