i can't tighten the hinge screws on my aluminum swinging screen door, the screws just spin without tightening. how can this be remedied?
It depends on the frame.  

If the frame is metal 


remove screws one by one
take some bare copper wires and insert them into the hole
put the screw in the middle of the hole with the copper wires on the outside
screw down until just about flush then cut the excess length from wires before finishing.


The screw should jamb the copper wires into the metal hole and allow the screw to grab.

If the frame is wood you can use wood pieces to do a similar thing.  Golf tees, wood match sticks, small pieces split from shims will all work.