True the walls

Here I am nailing the garage south wall top plate in.  The top plate ties different wall sections together and provides more rigidity to the walls.  Notice the solid lumber to my right that will hold up the steel beam in the garage.

The walls must be trued in all dimensions.  The rack of the wall is tough for one person to adjust.  I use a tie down strap to square up the rack so all the studs meet the top and bottom plates at right angles.  It's quick and easy.

Any guesses as to the name of this tool and its purpose?  Email your guess if you want