How to Fasten a Scissor Truss With a 2x4

Lay out the pre-constructed scissor truss. The truss will be shaped like an upside down "V" with boards running across the middle of it at an angle. Inspect the bottom of the vertical pieces of the truss and verify they are cut at an angle. They must be cut at an angle to be installed properly.

Measure the distance from the bottom of one side of the truss to the other. Position a ladder at the base of the roof you are building and measure the distance across the roof with a tape measure. Verify that the distance is the same as the truss so it can fit properly when you install it.

Cut a 2-by-4 to the size of the recorded measurement with a miter saw. Slide the 2-by-4 into the miter saw and cut off the end at a 45 degree angle. Turn the saw to 45 degrees in the opposite direction and cut off the 2-by-4 at the recorded measurement.

Run the 2-by-4 across the bottom of the truss and verify it fits together properly. Attach it to the truss with a mending plate. A mending plate is a small plate with spikes on one side to connect two pieces of lumber together. Set the mending plate down on top of the truss and the 2-by-4 and hammer it down to secure the two together. Repeat the process for the other side.

Measure out 16 inches from the base of either end of the house and position the truss in place. Secure it to the plates running underneath with exterior screws and a power drill. Space out the screws every 4 inches and secure the truss in place on both sides so it is secure to the plate underneath.