The side holds the trigger bar in position. If you remove the slide then the trigger bar becomes loose which may cause the spring to pop free. If you try to operate the trigger with the slide removed it will most surely pop loose.
![Image](http://i570.photobucket.com/albums/ss142/istbankodad/guns/mvc-003f.jpg)
Looking through the left side with the slide stop lever removed you can see the correct position of the spring on the trigger bar.
![Image](http://i570.photobucket.com/albums/ss142/istbankodad/guns/mvc-006f.jpg)
Another view right side showing the trigger bar removed. Notice the spring resting against the top of the frame. The spring should set on the bottom side of the bar groove.
![Image](http://i570.photobucket.com/albums/ss142/istbankodad/guns/mvc-00b7f.jpg)
With the trigger bar in place you can see the spring has pop loose and resting against the frame.
![Image](http://i570.photobucket.com/albums/ss142/istbankodad/guns/mvc-00b9f.jpg)
Getting the spring back on the bar is tricky. I use a nettle probe to pull the spring down and back while using my other hand to position the bar in place.
Hope this can be helpful.