I bought a good sized hand held circular saw that happened to have lift/fall adjustment for £30 off ebay and mounted it to the underside of a sheet of 18mm Birch ply using bolts and recesses T nuts left over from a previous speaker build.
I also bought some 1.0m long Steel rules from ebay for about £3 and routered them into the top of the ply and set them accurately with the guide up against the saw blade (I can adjust the position of the rules for blade changes/re-setup)

The L shaped guide is secured using a simple butterfly nut with a large rectangular plate below running in a shallow routered track to stop the bolt from spinning.

This has been on of my most succesfull constructions and when not in use it just leans up against my garage wall.
I experimented a lot before starting the DR and found every single panel to be mm accurate...very happy with the end result
You can alse see a guide along one edge formed again with 18mm birch that I use with a single track Panel Jig.
Because of the location of the Steel rule I could not fit another, but so far I have not had any problems using the single slide. Total cost was about £40
Deadly yes...Would I let my kids play near it...no way
DIY tastic