Step 1
Lift the aluminum frame's header and sides into the rough opening. Insert the tabs on the top of the sides into the grooves in the header's ends.
Step 2
Hold a level against the aluminum door frame's header. Raise or lower each side until the header is level. Slide wooden shims underneath the side jambs, if necessary, for additional support. Drive 1 5/8-inch screws through the header's guide holes.
Step 3
Hold a level against one of the sides. Position the side so it rests straight in the opening. Drive 1 5/8-inch screws through the side's guide holes.
Step 4
Check the other side with a level to make sure it is level in the opening. Secure this side in place with 1 5/8-inch screws through the guide holes.
Step 5
Cut off the shim's extending ends with a utility knife so they do not go past the aluminum door frame.