PS2

PS2 Controller Maintenance
To successfully reinstall the L and R 2 triggers to their original positions get the controller backing and push inwards on the triggers, they should come out with a click.

Once they are out put the backing on the controller but dont screw it back together just yet.

Make sure your contact points are sitting flat. if they are all you need to do is grab the triggers and put them in their positions.

To do this put the trigger in the casing and push it inwards from one side, it will slant into place leaving the other side to push in. do this to both triggers and your controller will work like new.

-- Azrael87 From answerbag.com