I watched a series of videos by mrbigrock. In some of them, he uses a tool that has a blade that extends from the body. He places the body against the work and uses the blade to set the location of the Festool rails relative to the edge of the work. The body is a medium blue so I don't think it's Festool or Woodpecker. Here's a link to the video. The tool appears about 1:30 in. Any idea who makes it or if there are similar tools on the market?
Link to youtube video
Link to youtube video