I have one of those tools with my machine. I do't think the light skrews in like a standard lightbulb. I think it needs to be just pushed in and twisted so tha the 2 little bumps on the side of the socket can fit in. The tool cups the light bulb so you have a grip. That end is about 1 inch long. The other end is a tool to pry/lift up the throat plate. I use it all the time to change to a straight stitch (single hole) plate.
Here's a link to some suggested ways to change the bulb without the tool.
http://www.pfaff-talk.net/chatroom/m...ad?thread=8804